Ember.js EmberRouter addObserver() Method

Ember.js is an open-source JavaScript framework used for developing large client-side web applications which is based on Model-View-Controller (MVC) architecture. Ember.js is one of the most widely used front-end application frameworks. It is made to speed up development and increase productivity. Currently, it is utilized by a large number of websites, including Square, Discourse, Groupon, Linked In, Live Nation, Twitch, and Chipotle.

The addObserver() method is used to register an observer for property and Observer will invoke the method and object whenever value of property value changes.

Syntax:

addObserver( key, target, method, sync );

Parameters:

• key: It name of property for which observer will register. 
• target: It is object which invoke whenever property change. 
• method: It is method which invoke on value change of property. 
• sync: This parameter indicates whether observer is sync or not.

Return: Observable.

Steps to Install and Run Ember.js:

Step 1: To run the following examples, you will need to have an ember project with you. To create one, you will need to install ember-cli first. Write the below code in the terminal:

npm install ember-cli

Step 2: Now, you can create the project by typing in the following piece of code:

ember new <project-name> --lang en

To start the server, type:

ember serve

Example 1: Type the following code to generate the route for this example:

ember generate route test1

app/components/arr.js

Javascript

import Component from '@glimmer/component';
import Ember from 'ember';
import { action, without, set, get } from '@ember/object';
export default Ember.Component.extend({
    value: 'Oxygen',
    init() {
        this._super(...arguments);
        this.addObserver('value', this, 'change');
    },
    change() {
        console.log('Value changed ')
    },
    list: [
        'Black Panthar',
        'Source_Code',
        'Infine',
        'Tenet',
        'SpiderHead',
        'The_Thing',
        'A_Quiet_Place',
        'The_Invisible_Man',
        'Looper',
        'Avtar',
    ],

    @action
    remove(data) {
        this.list.set('[]', this.list.without(data));
    },
    @action
    print(){
        let ans = this.list.get('[]');
        alert(ans.join('\n'))
    }
})

app/components/arr.hbs

HTML

<ul>
    <h3>{{yield}} </h3>
    {{#each this.list as |item|}}
    <li>{{item}}</li>
    {{/each}}
</ul>
<br />
{{input value=this.value}}
<br />
<input type="button" id="check-atIndex"
    value="Remove" {{action 'remove' this.value}} />
<br /><br />
<input type="button" id="print-item"
    value="Print All Items" {{action 'print' }} />

app/templates/test1.hbs

HTML

<Arr> <h3>Movies List : </h3></Arr>

Output:

Ember.js EmberRouter addObserver() Method

Example 2: Type the following code to generate the route for this example:

ember generate route test2

app/components/arr2.js

Javascript

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';
import Ember from 'ember';

let Student = Ember.Object.extend({

    // These will be supplied by `create`
    firstName: null,
    lastName: null,

    fullName: Ember.computed('firstName', 'lastName', function () {
        return `${this.firstName} ${this.lastName}`;
    }),

    Changed: Ember.observer('fullName', function () {
        console.log(`fullName changed to: ${this.fullName}`);
    }),
});

export default Ember.Component.extend({
    students: [
        Student.create({
            firstName: 'Balit',
            lastName: 'stark',
            Id: 'stu2',
        }),
        Student.create({
            firstName: 'Permu',
            lastName: 'scott',
            Id: 'stu0',
        }),
        Student.create({
            firstName: 'Sam',
            lastName: 'melo',
            Id: 'stu1',
        }),
        Student.create({
            firstName: 'Pokhu',
            lastName: 'Verma',
            Id: 'stu3',
        }),
        Student.create({
            firstName: 'Tanu',
            lastName: 'Agrawal',
            Id: 'stu4',
        }),
        Student.create({
            firstName: 'Arabh',
            lastName: 'Singh',
            Id: 'stu5',
        })
    ],

    @tracked
    value: 'Pokhu',

    @tracked
    value2: 'Pokhraj',

    @action
    print(data1, data2) {
        let ans = this.students.find(
            (item) => item.get('firstName') == data1)
        ans.set('lastName', data2)
    }
})

app/components/arr2.hbs

HTML

{{yield}}
<table>
    <tr>
        <th>Name</th>
        <th>Id</th>
    </tr>
    {{#each this.students as |detail|}}
    <tr>
        <td>{{detail.fullName}}</td>
        <td>{{get detail 'Id'}}</td>
    </tr>
    {{/each}}
</table>
<br />
{{input value=this.value}}

{{input value=this.value2}}
<br />
<input type="button" id="set-code"
    value="Update Student details"
    {{action 'print' this.value this.value2}} />

app/templates/test2.hbs

HTML

<Arr2><h3>Student's List :</h3></Arr2>

Output:

Ember.js EmberRouter addObserver() Method

Reference: https://api.emberjs.com/ember/4.6/classes/EmberRouter/methods/addObserver?anchor=addObserver