Ember.js Ember.Templates.helpers unless() 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 unless() method is used for conditional rendering. It is the inverse of if helper. It displays the value if the condition is false.

Syntax:

{{ unless condition }} 

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 unless1

app/components/arr2.js

Javascript

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

export default class extends Component {
    student = [{
        "name": "Sam Snehil",
        "age": 21
    },
    {
        "name": "Satyam Sahu",
        "age": 23
    },
    {
        "name": "Sohan Argrwal",
        "age": 25
    },
    {
        "name": "Sreya Sarma",
        "age": 19
    }
    ,
    {
        "name": "Satyam Sahu",
    }];


    print(item) {

        let ans = this.student.filterBy('name',item)
        alert(JSON.stringify(ans));
    }
}

app/components/arr2.hbs

HTML

{{yield}}
<table>
    <tr>
        <th>Name</th>
        <th>Age</th>
    </tr>
      {{#each this.student as |detail|}}

    {{#unless detail.age}}
    <tr>
            <td>{{get detail 'name'}}</td>
            <td>{{18}}</td>
        </tr>
    {{else}}
            <tr>
            <td>{{get detail 'name'}}</td>
            <td>{{get detail 'age'}}</td>
        </tr>
    {{/unless}}
    {{/each}}
</table>
<br/>
{{textarea value=this.value}}
<br/>
<input type="button"
    id="set-code"
    value="Introduce Student"
    {{action 'print' (mut this.value)}}/>

app/templates/unless1.hbs

HTML

<Arr2>
    <h1>
        List of Student :
    </h1>
</Arr2>
{{outlet}}

Output:

Ember.js Ember.Templates.helpers unless() Method

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

ember generate route unless2

app/components/arr.js

Javascript

import Component from '@glimmer/component';
import {tracked} from '@glimmer/tracking';
import { action, addObjects } from '@ember/object';
export default class CompactComponent extends Component {

    items = ['Oxygen',
        'Source Code',
        'Infine',
        'Tenet',
        'SpiderHead',
        'The Thing',
        'A Quiet Place',
        'The Invisible Man',
        'Looper',
        'Ad Astra',];

    @action
    remove(data) {
        this.items.removeObject(data);
    }
}

app/components/arr.hbs

HTML

{{#unless @show}}

This comoponent Don't Have block!!<br/>
{{else}}
<ul>
<h3>{{yield}} : </h3>
    {{#each this.items as |party|}}
        <li>{{party}}</li>
    {{/each}}
</ul>
<br />
{{textarea value=this.value}}
<br/>
<input
    type="button"
    id="check-atIndex"
    value="Remove"
    {{action "remove" this.value}}
/>
<br/><br/>
{{/unless}}

app/templates/unless2.hbs

HTML

<Arr @show={{true}}>
    List of items
</Arr>
{{outlet}}
<Arr/>

Output:

Ember.js Ember.Templates.helpers unless() Method

Reference: https://api.emberjs.com/ember/4.6/classes/Ember.Templates.helpers/methods/unless?anchor=unless