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frameworks-code-comparison

Frontend Frameworks Code Comparison

./assets/logos/angular.svg
./assets/logos/react.svg
./assets/logos/vue.svg

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Comparison of different approaches in writing web applications. Based on React, Angular, AngularJS and Vue.js. It is especially useful when migrating between frameworks or switching projects often.

All examples follow the current best practices and conventions that are used inside the community of a given framework. Angular code is written in TypeScript.

โš ๏ธ Work in progress! PRs and Feedback are welcome โš ๏ธ

Note regarding framework naming:

  • AngularJS refers to Angular v1.x
  • Angular refers to Angular v2+

See: http://angularjs.blogspot.com/2017/01/branding-guidelines-for-angular-and.html

Table of contents

Simple component

angular.js AngularJS

Since AngularJS 1.5 we have a new syntax (backported from Angular 2) to built component-based applications using component type.

export class ChangePasswordController { constructor($log, Auth, Notification) { 'ngInject'; this.$log = $log; this.Auth = Auth; this.Notification = Notification; } $onInit() { this.password = ''; } changePassword() { this.Auth.changePassword(this.password).then(() => { this.Notification.info('Password has been changed successfully.'); }).catch(error => { this.$log.error(error); this.Notification.error('There was an error. Please try again.'); }); } }

Every component has to be declared inside a module. After that, it will be available to every other component.

import angular from 'angular';
import template from './changePassword.html';
import ChangePasswordController from './changePassword.controller.scss';
import './changePassword.scss';

const component = {
  bindings: {},
  template,
  controller: ChangePasswordController,
};

export const module = angular
  .module('app.changePassword', [])
  .component('changePassword', component);

๐Ÿ”— https://docs.angularjs.org/guide/component

angular Angular

import { Component } from '@angular/core'; import { Logger } from 'services/logger'; import { Auth } from 'services/auth'; import { Notification } from 'services/notification'; @Component({ selector: 'change-password', templateUrl: './ChangePassword.component.html', styleUrls: ['./ChangePassword.component.scss'], }) export class ChangePasswordComponent { password: string = ''; constructor( private logger: Logger, private auth: Auth, private notification: Notification, ) {} changePassword() { this.auth.changePassword(this.password).subscribe(() => { this.notification.info('Password has been changes successfully'); }).catch(error => { this.logger.error(error); this.notification.error('There was an error. Please try again'); }); } }

Every component has to be declared inside a module in order to be used within this module’s other components (it’s not available outside of).

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { ChangePasswordComponent } from './change-password.component';

@NgModule({
  imports: [CommonModule],
  declarations: [ChangePasswordComponent],
})
export class ChangePasswordModule {}

๐Ÿ”— https://angular.io/api/core/Component

react React

import Logger from 'utils/logger'; import Auth from 'actions/auth'; import Notification from 'utils/notification'; export class ChangePassword { state = { password: '', }; changePassword() { Auth.changePassword(this.state.password).then(() => { Notification.info('Password has been changed successfully.'); }).catch(error => { Logger.error(error); Notification.error('There was an error. Please try again.'); }); } render() { return <div>{ /* template */ }</div>; } }

๐Ÿ”— https://reactjs.org/docs/react-component.html

vue Vue.js

import Vue from 'vue'; import Logger from 'utils/logger'; import Auth from 'actions/auth'; import Notification from 'utils/notification'; Vue.component('change-password', { template: '<div>{{ /* template */ }}</div>', data() { return { password: '', }; }, methods: { changePassword() { Auth.changePassword(this.state.password).then(() => { Notification.info('Password has been changed successfully.'); }).catch(error => { Logger.error(error); Notification.error('There was an error. Please try again.'); }); }, }, });

๐Ÿ”— https://vuejs.org/v2/guide/components.html

Dependency injection

angular.js AngularJS

In AngularJS the constructor is being used to inject dependencies, which is done implicitly by the $inject service.

The 'ngInject' annotation can be used, which allows automatic method annotation by the ng-annotate plugin (e.g. ng-annotate-loader for Webpack). This is essential to counter minification problems.

export class ChangePasswordController {
  constructor($log, Auth, Notification) {
    'ngInject';

    this.$log = $log;
    this.Auth = Auth;
    this.Notification = Notification;
  }

  handleEvent() {
    this.Notification.info('Password changed successfully');
    this.$log.info('Password changed successfully');
  }
}

๐Ÿ”— https://docs.angularjs.org/guide/di

angular Angular

You specify the definition of the dependencies in the constructor (leveraging TypeScript’s constructor syntax for declaring parameters and properties simultaneously).

import { Component } from '@angular/core';
import { Logger } from 'services/logger';
import { Auth } from 'services/auth';
import { Notification } from 'services/notification';

@Component({
  selector: 'change-password',
  templateUrl: './ChangePassword.component.html',
})
export class ChangePasswordComponent {
  constructor(
    private logger: Logger,
    private auth: Auth,
    private notification: Notification,
  ) {}

  handleEvent() {
    this.notification.info('Password changed successfully');
    this.logger.info('Password changed successfully');
  }
}

๐Ÿ”— https://angular.io/guide/dependency-injection

react React

There’s no special injection mechanism. ES2015 modules are used for dependency management.

import React, { Component } from 'react'; import Logger from 'utils/logger'; import Notification from 'utils/notification'; export class ChangePassword extends Component { handleEvent = () => { Notification.info('Password changed successfully'); Logger.info('Password changed successfully'); } render() { return <div>{ /* template */ }</div>; } }

vue Vue.js

Vue.js uses ES2015 modules for dependency management:

import Vue from 'vue'; import Logger from 'utils/logger'; import Notification from 'utils/notification'; Vue.component('change-password', { template: '<div>{{ /* template */ }}</div>', methods: { handleEvent() { Notification.info('Password changed successfully'); Logger.info('Password changed successfully'); }, }, });

There’s also provide and inject mechanism which is primarily provided for advanced plugin / component library use cases:

Parent component:

import Notification from 'utils/notification';
import Vue from 'vue';

new Vue({
  el: '#app',
  provide: {
    notification: Notification,
  },
});

Child component:

import Vue from 'vue'; Vue.component('change-password', { inject: ['notification'], template: '<div>{{ /* template */ }}</div>', methods: { handleEvent() { this.notification.info('Event handled successfully'); }, }, });

Templates

angular.js AngularJS

Templates in AngularJS are compiled by the $compile service.
Values of component properties must be one of the following:

  • string binding (defined as @)
  • expression binding (defined as <)
  • reference binding (defined as &)
<primary-button size="big" disabled="true" click="$ctrl.saveContent()"> Save </primary-button>

angular Angular

There are three kinds of attributes that can be passed:

  • text binding, e.g. size="string"
  • property binding, e.g. [disabled]="value"
  • event binding, e.g. (click)="eventHandler()"
<primary-button size="big" [disabled]="true" (click)="saveContent()"> Save </primary-button>

react React

Templates in React are written inside the JavaScript file using the JSX language. This allows us to utilize all JavaScript capabilities. JSX uses the uppercase and lowercase convention to distinguish between the user-defined components and DOM elements.

<PrimaryButton size="big" disabled onClick={ this.saveContent } > Save </PrimaryButton>;

vue Vue.js

Component properties can be passed in as:

  • literal (as strings) e.g. size="big"
  • dynamic (using v-bind or :shorthand with actual values) e.g. v-bind:disabled="true"

Events can be listened to using v-on or @shorthand combined with the event name, and a method name as the value, e.g v-on:click="saveContent".

<primary-button size="big" v-bind:disabled="true" v-on:click="saveContent" > Save </primary-button>

๐Ÿ”— https://vuejs.org/v2/guide/syntax.html

Interpolation

angular.js AngularJS

In AngularJS interpolation is the process of data-binding values of the scope to the HTML. You can also interpolate more complicated values e.g. expressions or function invocations.

<img ng-src="{{ $ctrl.image.url }}" alt="{{ $ctrl.image.alt }}" />

We use ng-src instead of the regular src attribute so that AngularJS can set it up before the browser will try to load the image.

Another way to “bind” data is to use ng-bind. This allows us to counter the issue with a raw state being displayed before AngularJS compiles the template.

<label> Enter name: <input type="text" ng-model="$ctrl.name"> </label> <span ng-bind="$ctrl.name"></span>

๐Ÿ”— https://docs.angularjs.org/guide/interpolation

angular Angular

Angular is similar to AngularJS, so we use double curly braces ({{ }}) for interpolation. Since Angular offers property binding you often have a choice to use it instead of interpolation.

<img [src]="image.url" alt="{{ image.alt }}" />

[src] presents property binding while the alt attribute is being interpolated.

๐Ÿ”— https://angular.io/guide/template-syntax#interpolation

react React

React uses single curly braces for interpolation. Any JavaScript can be interpolated.

<img src={ this.props.image.url } alt={ this.props.image.alt } />;

๐Ÿ”— https://reactjs.org/docs/introducing-jsx.html#embedding-expressions-in-jsx

vue Vue.js

<img :src="image.url" alt="{{ image.alt }}" />

You can also perform one-time interpolations that do not update on data change by using the v-once directive,

<span v-once>Hello {{ username }}!</span>

๐Ÿ”— https://vuejs.org/v2/guide/syntax.html#Interpolations

Handling DOM Events

angular.js AngularJS

Handlers of native events are bound using provided built-in directives e.g.
ng-click, ng-focus, ng-keypress.

class MenuTopbarController {
  $onInit() {
    this.selected = null;
  }

  handleClick(item) {
    if (this.selected !== item) {
      this.selected = item;
      if (typeof item.callback === 'function') {
        item.callback();
      }
    }
  }
}

const menuTopbar = {
  bindings: {
    items: '<',
  },
  template: require('./menuTopbar.html'),
  controller: MenuTopbarController,
};

angular.module('app')
  .component('menuTopbar', menuTopbar);
<ul> <li ng-repeat="item in $ctrl.items" ng-click="$ctrl.handleClick(item)"> {{ item.label }} </li> </ul>

๐Ÿ”— https://docs.angularjs.org/tutorial/step_12

angular Angular

There’s a special syntax for binding to element’s events with (). The target inside the () is an event we want to listen for.

export interface MenuItem {
  label: string;
  callback?: Function;
}

import { Component, Input, Output, EventEmitter } from '@angular/core';
import { MenuItem } from './menu-item.interface';

@Component({
  selector: 'menu-topbar',
  template: require('./menuTopbar.html'),
})
export class MenuTopbarComponent {
  private selected = null;
  @Input() items: MenuItem[];

  handleClick(item: MenuItem) {
    if (this.selected !== item) {
      this.selected = item;
      if (item.callback) {
        item.callback();
      }
    }
  }
}
<ul> <li *ngFor="let item of items" (click)="handleClick(item)"> {{ item.label }} </li> </ul>

To bind to component’s host element events, you can use HostListener decorator.

@Component({
  selector: 'menu-topbar',
  template: require('./menuTopbar.html'),
})
export class MenuTopbarComponent {
  @HostListener('mouseenter') onMouseEnter() {
    this.highlight('#DDD');
  }
  
  @HostListener('mouseleave') onMouseLeave() {
    this.highlight(null);
  }

  private highlight(color) {
    /* ... */
  }

react React

Handling events with React elements is very similar to handling events on DOM elements. There are two syntactic differences though.

  • React events are named using camelCase, rather than lowercase e.g. (onClick, onFocus, onKeyPress).
  • With JSX you pass a function as the event handler, rather than a string.

Your event handlers will be passed instances of SyntheticEvent, a cross-browser wrapper around the browserโ€™s native event. It has the same interface as the browserโ€™s native event, including stopPropagation() and preventDefault(), except the events work identically across all browsers.

import React, { Component } from 'react'; export class MenuTopbar extends Component { state = { selected: null, }; handleClick(item) { if (this.selected !== item) { this.setState({ selected: item }); if (item.callback) { item.callback(); } } } render() { return ( <ul> { this.props.items.map(item => ( <li key={ item.label } onClick={ () => this.handleClick(item) } > { item.label } </li> )) } </ul> ); } }

๐Ÿ”— https://reactjs.org/docs/handling-events.html

vue Vue.js

We can use the v-on directive (or @ shorthand) to listen to DOM events and run some JavaScript when theyโ€™re triggered.

Vue also provides event modifiers (directive postfixes denoted by a dot).

  • .stop – stopPropagation
  • .prevent – preventDefault
  • .capture – use capture mode
  • .self – only trigger handler if event.target is the element itself
  • .once – the event will be triggered at most once
Vue.component('menu-topbar', { data: { selected: null, }, methods: { handleClick: (item) => { if (this.selected !== item) { this.selected = item; if (item.callback) { item.callback(); } } }, }, });
<ul> <li v-for="item in items" :key="item.label" @click="handleClick(item)" > {{ item.label }} </li> </ul>

๐Ÿ”— https://vuejs.org/v2/guide/events.html

Inputs and Outputs

angular.js AngularJS

Inputs are defined by either @ (string binding) or < (one-way binding) while outputs are defined by the & symbol. Passing arguments requires you to use an object in a child component which is then mapped to function parameters defined in the template.

class UserPreviewComponent {
  $onInit() {
    this.editedUser = {
      name: this.user.name,
      email: this.user.email,
    };
  }

  submitEdit() {
    this.onEdit({ user: this.editedUser });
  }
}

const component = {
  bindings: {
    user: '<',
    onEdit: '&',
  },
  template: require('./userPreview.html'),
  controller: UserPreviewComponent,
};

export default angular.module.component('userPreview', component);
<form ng-submit="$ctrl.submitEdit()"> <input type="text" ng-model="$ctrl.editedUser.name"> <input type="email" ng-model="$ctrl.editedUser.email"> <input type="submit" value="Submit" /> </form>

In a parent component:

class SettingsComponent {
  user = {
    name: 'John Smith',
    email: 'john.smith@example.com',
  };

  editUser(user) {
    this.user = Object.assign({}, this.user, user);
    console.log('Name of the edited user is', user.name);
  }
}

const component = {
  template: require('./settings.html'),
  controller: SettingsComponent,
};

export default angular.module.component('settings', component);
<user-preview user="user" on-edit="editUser(user)"> </user-preview>

angular Angular

Inputs are defined using the @Input decorator while outputs using the @Output decorator.

Component({ selector: 'user-preview', template: require('./userPreview.html'), }) export class UserPreviewComponent { private editedUser: User; @Input() user: User; @Output() onEdit: EventEmitter = new EventEmitter<User>(); ngOnInit() { this.editedUser = { name: this.user.name, email: this.user.email, }; } submitEdit() { this.onEdit.emit(this.editedUser); } }
<form (ngSubmit)="submitEdit()"> <input type="text" [(ngModel)]="editedUser.name"> <input type="text" [(ngModel)]="editedUser.email"> <input type="submit" value="Submit" /> </form>

In a parent component:

@Component({
  selector: 'settings',
  template: require('./settings.html'),
})
export class SettingsComponent {
  user: User = {
    name: 'John Smith',
    email: 'john.smith@example.com',
  };

  editUser(user: User) {
    this.user = Object.assign({}, this.user, user);
    console.log('User has been edited: ', user);
  }
}
<user-preview [user]="user" (onEdit)="editUser($event)" ></user-preview>

๐Ÿ”— https://angular.io/guide/component-interaction

react React

import React, { Component } from 'react'; import PropTypes from 'prop-types'; import { User } from 'utils'; class UserPreviewComponent extends Component { submitEdit = () => { this.props.onEdit({ name: this.state.name, email: this.state.email, }); }; handleInputChange({ target }) { this.setState({ [target.name]: target.value, }); } render() { return ( <form onSubmit={ this.submitEdit }> <input type="text" name="name" value={ this.state.name } onChange={ this.handleInputChange } /> <input type="email" name="email" value={ this.state.email } onChange={ this.handleInputChange } /> <input type="submit" value="Submit" /> </form> ); } } UserPreviewComponent.propTypes = { user: PropTypes.instanceOf(User), onEdit: PropTypes.func, };

In a parent component:

import React, { Component } from 'react'; import { User } from 'utils'; export class SettingsComponent extends Component { state = { user: { name: 'John Smith', email: 'john.smith@example.com', }, }; editUser(user: User){ this.setState({ user: Object.assign({}, this.state.user, user), }); console.log('User has been edited: ', user); } render() { return ( <UserPreviewComponent user={ this.state.user } onEdit={ (user) => this.editUser(user) } /> ); } }

vue Vue.js

Child component:

Vue.component('child', { props: { class: { type: String, required: true, }, loading: Boolean, message: String, }, template: '<span v-bind:class="class" v-show="loading" v-text="message"></span>', });

Usage in the parent component:

<child class="small" :loading="true" message="Busy Loading!"></child>

๐Ÿ”— https://vuejs.org/v2/guide/components.html#Props

Default inputs

angular.js AngularJS

There’s no built-in mechanism for default inputs, so we assign them programmatically in the $onChanges hook.

class CoursesListController {
  $onChanges(bindings) {
    if (typeof bindings.displayPurchased.currentValue === 'undefined') {
      this.displayPurchased = true;
    }
    if (typeof bindings.displayAvailable.currentValue === 'undefined') {
      this.displayAvailable = true;
    }
  }
}

const component = {
  bindings: {
    displayPurchased: '<',
    displayAvailable: '<',
  },
  templateUrl: './coursesList.component.html',
  controller: CoursesListController,
};

export default component;

angular Angular

import { Component } from '@angular/core';

@Component({
  selector: 'courses-list',
  templateUrl: './coursesList.component.html',
})
export class CoursesListController {
  displayPurchased: boolean = true;
  displayAvailable: boolean = true;
}

react React

import React, { Component } from 'react'; import PropTypes from 'prop-types'; export class CoursesListController extends { Component } { static propTypes = { displayPurchased: PropTypes.bool, displayAvailable: PropTypes.bool, }; static defaultProps = { displayPurchased: true, displayAvailable: true, }; render() { return <div>{ /* template */ }</div>; } }

๐Ÿ”— https://reactjs.org/docs/typechecking-with-proptypes.html#default-prop-values

vue Vue.js

import Vue from 'vue'; Vue.component('courses-list', { template: '<div>{{ /* template */ }}</div>', props: { displayPurchased: { type: Boolean, default: true, }, displayAvailable: { type: Boolean, default: true, }, }, });

Lifecycle methods

angular.js AngularJS

$onInit()

Called when the component has been constructed and has its bindings have been initialized.

$postLink()

Called after the component and its children have been linked (mounted).

$onChanges(changes)

Called whenever one-way bindings are updated.

$doCheck()

Called on each turn of the digest cycle.

$onDestroy()

Called when the component (a controller with its containing scope) is being destroyed.

๐Ÿ”— https://docs.angularjs.org/api/ng/service/$compile

angular Angular

ngOnChanges()

Respond when Angular (re)sets data-bound input properties. The method receives a SimpleChanges object of current and previous property values.

Called before ngOnInit() and whenever one or more data-bound input properties change.

export class PeekABooComponent extends PeekABoo implements OnChanges {
  // only called for/if there is an @input variable set by parent.
  ngOnChanges(changes: SimpleChanges) {
    let changesMsgs: string[] = [];
    for (let propName in changes) {
      if (propName === 'name') {
        let name = changes['name'].currentValue;
        changesMsgs.push(`name ${this.verb} to "${name}"`);
      } else {
        changesMsgs.push(propName + ' ' + this.verb);
      }
    }
    this.logIt(`OnChanges: ${changesMsgs.join('; ')}`);
    this.verb = 'changed'; // next time it will be a change
  } 
}

ngOnInit()

Initialize the directive/component after Angular first displays the data-bound properties and sets the directive/component’s input properties.

Called once, after the first ngOnChanges().

export class PeekABoo implements OnInit {
  constructor(private logger: LoggerService) { }

  // implement OnInit's `ngOnInit` method
  ngOnInit() { this.logIt(`OnInit`); }

  logIt(msg: string) {
    this.logger.log(`#${nextId++} ${msg}`);
  }
}

ngDoCheck()

Detect and act upon changes that Angular can’t or won’t detect on its own.

Called during every change detection run, immediately after ngOnChanges() and ngOnInit().

export class PeekABooComponent extends PeekABoo implements DoCheck {
  ngDoCheck() { 
    this.logIt(`DoCheck`);
  }
}

ngAfterContentInit()

Respond after Angular projects external content into the component’s view.
Called once after the first ngDoCheck().

export class PeekABooComponent extends PeekABoo implements AfterContentInit {
  ngAfterContentInit() { this.logIt(`AfterContentInit`);  }
}

ngAfterContentChecked()

Respond after Angular checks the content projected into the component.

Called after the ngAfterContentInit() and every subsequent ngDoCheck()

export class PeekABooComponent extends PeekABoo implements AfterContentChecked {
  // Beware! Called frequently!
  // Called in every change detection cycle anywhere on the page
  ngAfterContentChecked() { this.logIt(`AfterContentChecked`); }
}

ngAfterViewInit()

Respond after Angular initializes the component’s views and child views.

Called once after the first ngAfterContentChecked().

export class AfterViewComponent implements  AfterViewChecked, AfterViewInit {  
  ngAfterViewInit() {
    // viewChild is set after the view has been initialized
    this.logIt('AfterViewInit');
    this.doSomething();
  }
}

ngAfterViewChecked()

Respond after Angular checks the component’s views and child views.

Called after the ngAfterViewInit and every subsequent ngAfterContentChecked()

export class AfterViewComponent implements  AfterViewChecked, AfterViewInit 
  ngAfterViewChecked() {
    // viewChild is updated after the view has been checked
    if (this.prevHero === this.viewChild.hero) {
      this.logIt('AfterViewChecked (no change)');
    } else {
      this.prevHero = this.viewChild.hero;
      this.logIt('AfterViewChecked');
      this.doSomething();
    }
  }
}

ngOnDestroy()

Cleanup just before Angular destroys the directive/component. Unsubscribe Observables and detach event handlers to avoid memory leaks.

Called just before Angular destroys the directive/component.

Directive({ selector: '[destroyDirective]' }) export class OnDestroyDirective implements OnDestroy { sayHello: number; constructor() { this.sayHiya = window.setInterval(() => console.log('hello'), 1000); } ngOnDestroy() { window.clearInterval(this.sayHiya); } }

react React

componentWillMount()

Is invoked just before rendering. Modifying the state here won’t trigger a re-render.

componentDidMount()

Is invoked after render. Useful for the initialization that require DOM nodes.

componentWillReceiveProps(nextProps)

Is only called after rendering, but before receiving new props. Because React may call this method without props changing, it is recommended to manually implement a check to see if there’s a difference.

shouldComponentUpdate(nextProps, nextState)

This method is called before receiving new props or a change of state. By default, it returns true which means re-rendering is triggered by any change. Modifying this method allows you to only re-render in intended scenarios.

componentWillUpdate(nextProps, nextState)

Is invoked whenever shouldComponentUpdate returns true before rendering. Note: You can’t use this.setState() here.

componentDidUpdate(prevProps, prevState)

Is invoked after rendering, but not after the initial render. This method is useful for manipulating the DOM when updated.

componentWillUnmount()

Is invoked immediately before a component is unmounted and destroyed. Useful for resource cleanup.

componentDidCatch(error,info)

Is invoked when Javascript throws an error anywhere in the component’s tree. Useful for catching errors, showing a fallback interface, and logging errors without breaking the entire application.

vue Vue.js

beforeCreate

Called synchronously immediately after the instance has been initialized, but before data observation and event/watcher setup. On every Vue instance lifecycle, this points to the vm instance itself.

new Vue({
  beforeCreate: function () {
    console.log('this method called before instance created')
  }
})

created

Called synchronously after the instance is created. At this stage, the instance has finished processing the options, which means the following have been set up: data observation, computed properties, methods, watch/event callbacks. However, the mounting phase has not been started, and the $el property will not be available yet.

new Vue({
  created: function () {
    console.log('this method called after instance created')
  }
})

beforeMount

Called right before the mounting begins: the render function is about to be called for the first time.

This hook is not called during server-side rendering.

new Vue({
  beforeMount: function () {
    console.log('this method called before mounting an instance')
  }
})

mounted

Called after the instance has been mounted, where el is replaced by the newly created vm.$el. If the root instance is mounted to an in-document element, vm.$el will also be in-document when mounted is called.

Note that mounted does not guarantee that all child components have also been mounted. If you want to wait until the entire view has been rendered, you can use vm.$nextTick inside of mounted:

new Vue({
  mounted: function () {
    this.$nextTick(function () {
      // Code that will run only after the
      // entire view has been rendered
    })
  }
})

beforeUpdate

Called whenever the data changes, before the virtual DOM is re-rendered and patched.

You can perform further state changes in this hook and they will not trigger additional re-renders.

This hook is not called during server-side rendering.

updated

Called after a data change causes the virtual DOM to be re-rendered and patched.

The componentโ€™s DOM will have been updated when this hook is called, so you can perform DOM-dependent operations here. However, in most cases you should avoid changing state inside the hook.

Note that updated does not guarantee that all child components have also been re-rendered. If you want to wait until the entire view has been re-rendered, you can use vm.$nextTick inside of updated:

updated: function () {
  this.$nextTick(function () {
    // Code that will run only after the
    // entire view has been re-rendered
  })
}

activated

Called when a kept-alive component is activated.

This hook is not called during server-side rendering.

deactivated

Called when a kept-alive component is deactivated.

This hook is not called during server-side rendering.

beforeDestroy

Called right before a Vue instance is destroyed. At this stage the instance is still fully functional.

This hook is not called during server-side rendering.

destroyed

Called after a Vue instance has been destroyed. When this hook is called, all directives of the Vue instance have been unbound, all event listeners have been removed, and all child Vue instances have also been destroyed.

This hook is not called during server-side rendering.

errorCaptured

Called when an error from any descendent component is captured.

Conditional rendering

angular.js AngularJS

Angularjs 1.x has three ways to perform conditional rendering: ng-if, ng-switch and ng-hide/ng-show.

export class RegistrationController {
  registrationCompleted = false;
  displaySpecialOffer = false;
  displayStatus = 'Registered';
}
<div ng-if="displaySpecialOffer"> <special-offer></special-offer> </div> <div ng-switch="displayStatus"> <div ng-switch-when="Registered"> <registration-completed></registration-completed> </div> </div> <div ng-show="displaySpecialOffer"> <special-offer></special-offer> </div> <div ng-hide="displaySpecialOffer"> <special-offer></special-offer> </div>

angular Angular

Since Angular 4.0.0, alongside standard ngIf, it is possible to use ngIf;else or ngIf;then;else using <ng-template> with an alias #aliasName.

import { Component } from '@angular/core';

@Component({
  selector: 'registration',
  template: '',
})
export class RegistrationComponent {
  registrationCompleted: boolean = false;
  displaySpecialOffer: boolean = false;
}
<div *ngIf="displaySpecialOffer"> <special-offer></special-offer> </div> <div *ngIf="registrationCompleted;else registrationForm"> <registration-completed></registration-completed> </div> <ng-template #registrationForm> <registration-form></registration-form> </ng-template>

๐Ÿ”— https://angular.io/api/common/NgIf

react React

The most common approach to conditional rendering is by using the ternary operator:
{ condition ? <Component /> : null }

import React, { Component } from 'react'; import PropTypes from 'prop-types'; export class Registration extends Component { state = { registrationCompleted: false, }; propTypes = { displaySpecialOffer: PropTypes.bool, } render() { return ( <div> { this.props.displaySpecialOffer ? <SpecialOffer /> : null } { this.state.registrationCompleted ? ( <RegistrationCompleted /> ) : ( <RegistrationForm /> ) } </div> ); } }

vue Vue.js

Vue.js has three directives to perform conditional rendering: v-if, v-else-if and v-else.

<template> <section v-if="registrationCompleted && !displaySpecialOffer"> <registration-completed /> </section> <section v-else-if="registrationCompleted && displaySpecialOffer"> <special-offer /> <registration-completed /> </section> <section v-else> <registration-form /> </section> </template>

๐Ÿ”— https://vuejs.org/v2/guide/conditional.html

Lists

angular.js AngularJS

ngRepeat

export class BookListComponentCtrl {
  constructor() {
    this.books = [
      {
        id: 1,
        title: 'Eloquent JavaScript',
        author: 'Marijn Haverbeke',
      },
      {
        id: 2,
        title: 'JavaScript: The Good Parts',
        author: 'Douglas Crockford',
      },
      {
        id: 3,
        title: 'JavaScript: The Definitive Guide',
        author: 'David Flanagan',
      },
    ];
  }
}
<ul> <li ng-repeat="book in $ctrl.books track by book.id"> {{ book.title }} by {{ book.author }} </li> </ul>

angular Angular

ngFor

export interface Book {
  id: number;
  title: string;
  author: string;
}
import { Component } from '@angular/core'; import { Book } from './book.interface'; @Component({ selector: 'book-list', template: ` <ul> <li *ngFor="let book of books; trackBy: trackById"> {{ book.title }} by {{ book.author }} </li> </ul> ` }) export class BookListComponent { this.books: Book[] = [ { id: 1, title: "Eloquent JavaScript", author: "Marijn Haverbeke" }, { id: 2, title: "JavaScript: The Good Parts", author: "Douglas Crockford" }, { id: 3, title: "JavaScript: The Definitive Guide", author: "David Flanagan" } ]; trackById(book) { return book.id; } }

react React

Lists and Keys

import React, { Component } from 'react'; export class BookList extends Component { state = { books: [ { id: 1, title: 'Eloquent JavaScript', author: 'Marijn Haverbeke', }, { id: 2, title: 'JavaScript: The Good Parts', author: 'Douglas Crockford', }, { id: 3, title: 'JavaScript: The Definitive Guide', author: 'David Flanagan', }, ], }; render() { const { books } = this.state; return ( <ul> { books.map(book => { return ( <li key="{ book.id }"> { book.title } by { book.author } </li> ); }) } </ul> ); } }

vue Vue.js

<template> <ul> <li v-for="book in books" :key="book.id"> {{ book.title }} by {{ book.author }} </li> </ul> </template>

export default {
  data() {
    return {
      books: [
        {
          id: 1,
          title: 'Eloquent JavaScript',
          author: 'Marijn Haverbeke',
        },
        {
          id: 2,
          title: 'JavaScript: The Good Parts',
          author: 'Douglas Crockford',
        },
        {
          id: 3,
          title: 'JavaScript: The Definitive Guide',
          author: 'David Flanagan',
        },
      ],
    };
  },
};

Filters

angular.js AngularJS

AngularJS provides filters to transform data. There are several built-in filters available and you can make your own custom filters as well.

Filters can be applied to view templates using the following syntax:

<h1>{{ price | currency }}</h1>

Chaining of filters is also possible:

<h1>{{ name | uppercase | appendTitle }}</h1>

Custom Filters:

angular.module('app', []) .filter('reverse', function() { return (input = '', uppercase = false) => { const out = input.split('').reverse().join(''); return uppercase ? out.toUpperCase() : out; }; });

๐Ÿ”— https://docs.angularjs.org/guide/filter

angular Angular

In Angular filters are called pipes. The built-in pipes available in Angular are: DatePipe, UpperCasePipe, LowerCasePipe, CurrencyPipe, and PercentPipe.

Apart from the built-in pipes, you can create your own, custom pipes.

Create a custom pipe:
this pipe transforms a given URL to a safe style URL, that way it can be used in hyperlinks, for example or <iframe src>, etc..

import { Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer} from '@angular/platform-browser';

@Pipe({ name: 'safe' })
export class SafePipe implements PipeTransform {
  constructor(public sanitizer: DomSanitizer) {}
  transform(url) {
    return this.sanitizer.bypassSecurityTrustResourceUrl(url);
  }
}

Use the custom pipe in a template:
The given someUrl is filtered through the safe pipe which transforms it trough the DomSanitizer function bypassSecurityTrustResourceUrl.

<iframe [src]="someUrl | safe"></iframe>

Note: [src] above is an input to the component which ‘lives’ above the iframe.

๐Ÿ”— https://angular.io/guide/pipes

react React

React doesn’t provide any specific filtering mechanism. This can simply be achieved by using ordinary JavaScript functions:

export function reverse(input = '', uppercase = false) {
  const out = input.split('').reverse().join('');

  return uppercase ? out.toUpperCase() : out;
}
import React, { Component } from 'react'; import { reverse } from 'utils'; export class App extends Component { render() { return ( <div> { reverse(this.props.input) } </div> ); } }

Filter chaining can be achieved using function composition:

<div> { truncate(reverse(this.props.input)) } </div>;

vue Vue.js

Vue.js provides filters to allow for simple text formatting. The filter utilizes the | character which is appended to the expression followed by the filter’s name. Vue does not come with any pre-built filters.

Filters can be used within mustache interpolations:

<h1>{{ name | lowercase }}</h1>

Filters can also be used within the v-bind directive:

<div v-bind:slug="slug | formatSlug"></div>

When creating filters, the function always receives the expression’s value:

new Vue({ el: '#app', template: '<p> {{ message | lowercase }} </p>', filters: { lowercase(word) { return word.toLowerCase(); }, }, data: { message: 'Hello World', }, });

Filters can also be chained:

<p>{{ description | lowercase | truncate }}</p>

Filters can be created locally like the above example and only be available within that component. Filters can also be declared globally:

Vue.filter('lowercase', word => word.toLowerCase());

For global filters to work, they should be declared before the Vue instance.

๐Ÿ”— https://vuejs.org/v2/guide/filters.html

Child nodes

angular.js AngularJS

Inside a component, we have access to the child node by injecting $element to the controller. This object contains a jqLite wrapped instance of the DOM element. Accessing $element[0] will return the bare DOM element.

Transclusion is also supported – using ng-transclude (See Transclusion and Containment section).

class TextInputController { constructor($element) { 'ngInject'; this.$element = $element; } // The $element can be used after the link stage $postLink() { const input = this.$element.find('input'); input.on('change', console.log); } } const component = { controller: TextInputController, template: ` <div> <input type="text" /> </div> `, };

angular Angular

Angular provides two ways to deal with child nodes: ViewChild and ContentChild. They both have the same purpose, but there are different use cases for them.

  • ViewChild works with the internal DOM of your component, defined by you in the component’s template. You have to use the @ViewChild decorator to get the DOM element reference.

  • ContentChild works with de DOM supplied to your component by its end-user (See Transclusion and Containment). You have to use the @ContentChild decorator to get the DOM element reference.

import { Component, Input, ViewChild, ContentChild, AfterViewInit, AfterContentInit, } from '@angular/core'; @Component({ selector: 'child', template: ` <p>Hello, I'm your child #{{ number }}!</p> `, }) export class Child { @Input() number: number; } @Component({ selector: 'parent', template: ` <child number="1"></child> <ng-content></ng-content> `, }) export class Parent implements AfterViewInit, AfterContentInit { @ViewChild(Child) viewChild: Child; @ContentChild(Child) contentChild: Child; ngAfterViewInit() { // ViewChild element is only available when the // ngAfterViewInit lifecycle hook is reached. console.log(this.viewChild); } ngAfterContentInit() { // ContentChild element is only available when the // ngAfterContentInit lifecycle hook is reached. console.log(this.contentChild); } } @Component({ selector: 'app', template: ` <parent> <child number="2"></child> <child number="3"></child> </parent> `, }) export class AppComponent { }

ViewChild and ContentChild only work with a single DOM element. You can use ViewChildren and ContentChildren in order to get multiple elements. Both return the elements wrapped in a QueryList.

react React

In React, we have two options to deal with child nodes: refs and children. With refs, you have access to the real DOM element. The children property lets you manipulate the underlying React elements.

refs

ref is a special attribute we can pass to a React element that receives a callback and call it with the corresponding DOM node.

import React, { Component } from 'react'; // In order to access child nodes from parents, we can pass the `ref` callback // to the children as props. const TextInput = ({ inputRef }) => ( <div> <input ref={inputRef} type="text" /> </div> ); class Parent extends Component { componentDidMount() { // Refs are only executed after mounting and unmounting. Now `this.textInput` // references a real DOM node. So, we can use the raw DOM API // (to focus the input, for example) this.textInput.focus(); } render() { // The child's `inputRef` prop receives the `ref` callback. // We can use the callback to store the DOM element in an instance variable. return ( <div> <label>This is my child: </label> <TextInput inputRef={node => { this.textInput = node; }} /> </div> ); } }

children

children is a special prop available in all React component instances. You can use it to control how and where the underlying React elements will be rendered.

import React, { Component } from 'react'; // children is just a prop. In this case, the value of `children` will be // what you pass to the <Heading /> component as a child node. const Heading = ({ children }) => ( <h1 className="Heading"> {children} </h1> ); // `this.props.children` refers to whatever is a valid node inside the <Layout /> element. class Layout extends Component { render() { return ( <div class="Layout"> {this.props.children} </div> ); } } const App = () => ( <div> <Heading>I am the child!</Heading> <Layout> We are {'the'} <strong>Children!</strong> </Layout> </div> );

vue Vue.js

TODO

Transclusion and Containment

Basic

angular.js AngularJS

angular.module('app.layout', []) .component('layout', { bindings: { theme: '@', }, controller: LayoutController, transclude: true, template: ` <div ng-class="'theme-' + $ctrl.theme"> <ng-transclude></ng-transclude> </div> `, }).component('pageContent', { template: '<div>Some content</div>', }).component('pageFooter', { template: '<footer>Some content</footer>', });
<layout theme="dark"> <page-content></page-content> <page-footer></page-footer> </layout>

angular Angular

Component({ selector: 'layout', template: ` <div> <ng-content></ng-content> </div> `, }) export class Layout {} @Component({ selector: 'page-content', template: '<div>Some content</div>', }) export class PageContent {} @Component({ selector: 'page-footer', template: '<footer>Some content</footer>', }) export class PageFooter {}
<layout> <page-content></page-content> <page-footer></page-footer> </layout>

react React

const Layout = ({ children, theme }) => ( <div className={`theme-${theme}`}> {children} </div> ); const PageContent = () => ( <div>Some content</div> ); const PageFooter = () => ( <div>Some content</div> ); <Layout theme='dark'> <PageContent /> <PageFooter /> </Layout>;

vue Vue.js

TODO

Multiple slots

angular.js AngularJS

angular.module('app.layout', []) .component('landingSection', { bindings: {}, controller: LandingSectionController, transclude: { contentSlot: '?content', // '?' indicates an optional slot iconSlot: '?icon', }, template: ` <div> <span ng-transclude="contentSlot"></span> <div> <span ng-transclude="iconSlot">This is the default value</span> </dev> </div> `, }).component('pageContent', { template: '<div>Some content</div>', });
<div> <h1>Page title</h1> <landing-section> <page-content></page-content> </landing-section> </div>

angular Angular

TODO

react React

const Layout = ({ children, theme }) => ( <div className={`theme-${theme}`}> <header>{children.header}</header> <main>{children.content}</main> <footer>{children.footer}</footer> </div> ); const Header = () => ( <h1>My Header</h1> ); const Footer = () => ( <div>My Footer</div> ); const Content = () => ( <div>Some fancy content</div> ); <Layout theme='dark'> {{ header: <Header />, content: <Content />, footer: <Footer />, }} </Layout>;

vue Vue.js

App layout:

<div class="container"> <header> <slot name="header"></slot> </header> <main> <slot></slot> </main> <footer> <slot name="footer"></slot> </footer> </div>

Parent markup:

<app-layout> <h1 slot="header">Here might be a page title</h1> <p>A paragraph for the main content.</p> <p>And another one.</p> <p slot="footer">Here's some contact info</p> </app-layout>

Result:

<div class="container"> <header> <h1>Here might be a page title</h1> </header> <main> <p>A paragraph for the main content.</p> <p>And another one.</p> </main> <footer> <p>Here's some contact info</p> </footer> </div>

๐Ÿ”— https://vuejs.org/v2/guide/components.html#Named-Slots

Class toggling

angular.js AngularJS

The ng-class directive allows you to dynamically set CSS classes on an HTML element.

<main-header ng-class="{ 'mainNavbar--fluid': $ctrl.isFluid }"> ... </main-header>

angular Angular

In Angular, the ngClass directive works similarly. It includes/excludes CSS classes based on an expression.

<main-header [ngClass]="{ 'mainNavbar--fluid': isFluid }"> ... </main-header>

react React

The React approach allows us to construct className string with JavaScript.

<MainHeader className={ this.props.isFluid ? 'mainNavbar--fluid' : '' } />;

Many utility libraries have emerged – classnames being among the most popular.

class App { /* ... */ render() { const classNames = classNames({ 'mainNavbar--fluid': this.props.isFluid, }); return ( <MainHeader className={ classNames } /> ); } }

vue Vue.js

<main-header v-bind:class="{ 'mainNavbar--fluid': isFluid }" >

๐Ÿ”— https://vuejs.org/v2/guide/class-and-style.html

Data binding

angular.js AngularJS

The ng-model directive binds a form control to a property in the controller. This provides two-way binding.

import angular from 'angular';
import template from './registration.html';

class RegistrationController {
  $onInit() {
    this.name = '';
  }
}

const component = {
  bindings: {},
  template,
  controller: RegistrationController,
};

export const module = angular
  .module('app.registration', [])
  .component('registration', component);
<input ng-model="$ctrl.name" /> <p>Name: {{ $ctrl.name }}</p>

angular Angular

We use [(ngModel)] to have a two-way data binding inside our forms. The value in the UI will always be synced with the domain model in the component.

import { Component } from '@angular/core';

@Component({
  selector: 'registration',
  templateUrl: require('registration.component.html'),
})
export class RegistrationComponent {
  name: string = '';
}
<input [(ngModel)]="name" /> <p>Name: {{ name }}</p>

๐Ÿ”— https://angular.io/guide/template-syntax#two-way-binding

react React

TODO

vue Vue.js

You can use the v-model directive to create two-way data bindings on form input and textarea elements. It automatically picks the correct way to update the element based on the input type. Although a bit magical, v-model is essentially syntax sugar for updating data on user input events, plus special care for some edge cases.

๐Ÿ”— https://vuejs.org/v2/guide/forms.html

Forms

angular.js AngularJS

class SignInController {
  constructor(Auth) {
    'ngInject';

    this.Auth = Auth;
  }

  $onInit() {
    this.email = '';
    this.password = '';
  }

  submit() {
    Auth.signIn(this.email, this.password);
  }
}
<form name="$ctrl.form"> <label> Email: <input type="text" ng-model="$ctrl.email" /> </label> <label> E-mail: <input type="email" ng-model="$ctrl.password" /> </label> <input type="submit" ng-click="$ctrl.submit()" value="Save" /> </form>

angular Angular

Angular offers two ways to build forms:

The former uses a reactive (or model-driven) approach to build forms. The latter allows you to build forms by writing templates in the Angular template syntax with the form-specific directives and techniques.

react Reactive forms example

import { Component, OnInit } from '@angular/core'; import { FormGroup, FormBuilder } from '@angular/forms'; @Component({ selector: 'reactive-form', template: ` <div> <form [formGroup]="form" (ngSubmit)="onSubmit(form.value, form.valid)" novalidate> <div> <label> Name: <input type="text" formControlName="name"> </label> </div> <div> <label> Email: <input type="email" formControlName="email"> </label> </div> </form> </div> ` }) export class ReactiveFormComponent implements OnInit { public form: FormGroup; constructor(private formBuilder: FormBuilder) { } ngOnInit() { this.form = this.formBuilder.group({name: [''], email: ['']}); } }

Template-driven forms example

import { Component } from '@angular/core'; @Component({ selector: 'template-driven-form', template: ` <div> <form (ngSubmit)="onSubmit()" #templateDrivenForm="ngForm" novalidate> <div> <label> Name: <input type="text" [(ngModel)]="model.name" required> </label> </div> <div> <label> Email: <input type="email" [(ngModel)]="model.email" required> </label> </div> <button type="submit" [disabled]="!templateDrivenForm.form.valid">Submit</button> </form> </div> ` }) export class TemplateDrivenFormComponent { public model = { name: '', email: '' }; }

The novalidate attribute in the <form> element prevents the browser from attempting native HTML validations.

react React

Two techniques exists in React to handle form data: Controlled Components and Uncontrolled Components. A controlled component keeps the input’s value in the state and updates it via setState(). While in an uncontrolled component, form data is handled by DOM itself and referenced via ref. In most cases, it is recommended to use controlled components.

import React, { Component } from 'react'; export default class ReactForm extends Component { state = { email: '', password:'', }; handleChange = ({ name, value}) => { if (name === 'email') { this.setState({ email: value }); } else if (name === 'password') { this.setState({ password: value }); } }; render() { return ( <form> <label> Email: <input name="email" type="email" value= {this.state.email } onChange={ this.handleChange } /> </label> <label> Password: <input name="password" type="password" value={ this.state.password } onChange={ this.handleChange } /> </label> </form> ); } }

๐Ÿ”— https://reactjs.org/docs/forms.html

vue Vue.js

<template> <form v-on:submit.prevent="onSubmit"> <label> Email: <input type="email" v-model="email"> </label> <label> Password: <input type="password" v-model="password" /> </label> <button type="submit">Send</button> </form> </template> <script> import Auth form './util/auth.js'; export default { data() { return { email: '', password: '' } }, methods: { onSubmit() { Auth.signIn(this.email, this.password); } } } </script>

๐Ÿ”— https://vuejs.org/v2/guide/forms.html

Styling

angular.js AngularJS

Generally you will use a preprocessor (e.g. Sass) and assign appropriate classes to the elements.

The ng-style directive allows you to set custom CSS styles dynamically.

class HeaderController {
  constructor(ThemeProvider) {
    'ngInject';

    this.ThemeProvider = ThemeProvider;
    this.headerStyles = {};
  }

  $onInit() {
    this.headerStyles.color = ThemeProvider.getTextPrimaryColor();
  }
}
<h1 ng-style="$ctrl.headerStyles" class="Header"> Welcome </h1>

angular Angular

When defining Angular components you may also include the CSS styles that will go with the template. By default the styles will be compiled as shadow DOM, which basically means you don’t need any namespacing strategy for CSS classes.

The ngStyle directive allows you to set custom CSS styles dynamically.

@Component({
  selector: 'ng-header',
  template: require('./header.html'),
  styles: [require('./header.scss')],
})
export class HeaderComponent {
  headerStyles = {};

  constructor(private themeProvider: ThemeProvider) {}

  ngOnInit() {
    this.headerStyles.color = ThemeProvider.getTextPrimaryColor();
  }
}
<h1 [ngStyle]="headerStyles" class="Header"> Welcome </h1>

.Header {
    font-weight: normal;
}

๐Ÿ”— https://angular.io/guide/component-styles

react React

In the React community there are many approaches to styling your app, ranging from traditional preprocessors (like in the Angular world) to so-called CSS in JS. The most popular include:

To dynamically apply styles you can directly pass an object to the style attribute.

export class HeaderComponent { state = { color: null, }; componentDidMount() { this.setState({ color: ThemeProvider.getTextPrimaryColor(), }); } render() { return ( <h1 styles={ { color: this.state.color } }> Welcome </h1> ); } }

vue Vue.js

When using Single File Components you can simply style a component inside the <style> tag. When the tag has the scoped attribute, its CSS will apply to elements of the current component only.

To bind styles dynamically you can use the v-bind:style directive.

<template> <h1 class="Header" v-bind:style="headerStyles"> Welcome </h1> </template> <script> const ThemeProvider = require('./utils/themeProvider'); module.exports = { data() { return { headerStyles: { color: null, } }; }, created() { this.headerStyles.color = ThemeProvider.getTextPrimaryColor(); }, }; </script> <style scoped> .Header { font-weight: normal } </style>

Inject HTML template

Also known as innerHTML.

angular.js AngularJS

By default, the HTML content will be sanitized using the $sanitize service. To utilize this functionality, you need to include ngSanitize in your module’s dependencies. Read more

<p ng-bind-html="$ctrl.article.content"></p>

angular Angular

The values are automatically sanitized before displaying them using DomSanitizer.

<p [innerHTML]="article.content"></p>

react React

All string values are sanitized before being inserted into the DOM. No more details are currently available.
You need to pass an object containing the __html property with the desired template contents.

<p dangerouslySetInnerHTML={ { __html: article.content } } />;

vue Vue.js

The content passed to v-html is not being sanitized. You have to use an external library, e.g. sanitize-html.

<div v-html="article.content"></div>
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