Ember.js ArrayProxy 长度属性

Ember.js 是一个开源的JavaScript框架，用于开发基于模型-视图-控制器（MVC）架构的大型客户端Web应用程序。Ember.js是最广泛使用的前端应用程序框架之一。它旨在加快开发速度和提高工作效率。目前，它被许多网站使用，包括Square、Discourse、Groupon、Linked In、Live Nation、Twitch和Chipotle。

length属性 是一个显示数组中元素总数的属性。

语法：

Array.length;

参数：

Array： 这是我们想要获取长度的数组。

安装和运行Ember.js的步骤：

要运行以下示例，您需要拥有一个Ember项目。要创建一个项目，您首先需要安装ember-cli。在终端中输入以下代码：

npm install ember-cli

现在你可以通过输入以下代码来创建项目：

ember new <project-name> --lang en

启动服务器，输入：

ember serve

示例1： 输入以下代码以生成此示例的路由：

ember generate route len1

app/routes/len1.js

import Route from "@ember/routing/route"; 
  
export default class StudentsRoute extends Route { 
    partyItems = [ 
        'Digital Camera', 
        'Jugs, cups & straws', 
        'Balloons', 
        'Scissors', 
        'Cold Drink', 
        'Table Confetti', 
        'Party Hats', 
        'Wine', 
        'Napkins', 
        'Party Plates', 
        'Speakers', 
        'Music System', 
        'Cups', 
    ]; 
    len; 
    model() { 
        return this.partyItems; 
    } 
    setupController(controller, model) { 
        super.setupController(controller, model); 
        controller.set("partyItems", this.partyItems); 
        controller.set("len", this.len); 
        controller.set("item", this.item); 
    } 
}

app/controllers/len1.js

import Ember from "ember"; 
  
export default Ember.Controller.extend({ 
    actions: { 
        show_first(){ 
            let ans = this.partyItems.get('firstObject') ; 
            alert(ans) 
        }, 
        show_last() { 
            let ans = this.partyItems.get('lastObject'); 
            alert(ans) 
              }, 
        show_len() { 
            let S_len = this.partyItems.length; 
            this.set('len',S_len) 
            alert('Length of List is '+this.len); 
        }, 
        check_items(data ){ 
            let temp = this.partyItems.without(data) 
            alert(temp.join('\n')) 
        }, 
    show() { 
      let temp = this.partyItems.get('[]'); 
      alert(temp.join('\n')) 
        }, 
    }, 
});

app/templates/len1.hbs

{{page-title "length"}} 
<h3>List of Items: </h3> 
  
<table> 
<ul>     
    {{#each @model as |student|}} 
      
        <li>{{student}}</li> 
      
    {{/each}} 
    </ul> 
</table> 
<br /><br /> 
<div> 
    <label>Enter Item: </label> 
    {{input value=this.temp}} 
</div> 
<input 
    type="button"
    id="check-atIndex"
    value="Print Except this Item"
    {{action "check_items" this.temp}} 
/> 
<br /><br /> 
<input 
    type="button"
    id="show-item"
    value="Pop up All Items"
    {{action "show"}} 
/> 
<br /><br /> 
<input 
    type="button"
    id="first-item"
    value="Show First Item"
    {{action "show_first"}} 
/> 
<br /><br /> 
<input 
    type="button"
    id="show-item2"
    value="Show Last Item"
    {{action "show_last"}} 
/> 
  
<br /><br /> 
<input 
    type="button"
    id="print-list"
    value="Print length of List"
    {{action "show_len"}} 
/> 
{{outlet}}

输出： 访问 localhost:4200/len1 查看输出

Ember.js ArrayProxy 长度属性

示例2： 输入以下代码来生成这个示例的路由：

ember generate route len2

app/routes/len2.js

import Route from '@ember/routing/route'; 
  
export default class PartyRoute extends Route { 
    partyItems = [ 
        'Oxygen', 
        'Source Code', 
        'Infine', 
        'Tenet', 
        'SpiderHead', 
        'The Thing', 
        'A Quiet Place', 
        'The Invisible Man', 
        'Looper', 
        'Ad Astra'
    ]; 
    item; 
    idx; 
    len; 
    model() { 
        return this.partyItems; 
    } 
    setupController(controller, model) { 
        super.setupController(controller, model); 
        controller.set('partyItems', this.partyItems); 
        controller.set('item', this.item); 
        controller.set('idx', this.idx); 
        controller.set('len', this.len); 
    } 
}

app/controllers/len2.js

import Ember from 'ember'; 
import { } from '@ember/array'; 
  
export default Ember.Controller.extend({ 
    actions: { 
        remove_Item(item) { 
            this.partyItems.set('[]', 
            this.partyItems.without(item)); 
        }, 
        print_len() { 
            alert( this.partyItems.length) 
              
        }, 
        print_first() { 
            let ans = this.partyItems.get('firstObject'); 
            alert(ans) 
        }, 
        print_last() { 
            let ans = this.partyItems.get('lastObject'); 
            alert(ans) 
        }, 
    }, 
});

app/templates/len2.hbs

{{page-title "length"}} 
<h3>Here is a list of items: </h3> 
<ul> 
    {{#each @model as |party|}} 
        <li>{{party}}</li> 
    {{/each}} 
</ul> 
<br /> 
<div> 
    <label>Enter value: </label> 
    {{input value=this.item}} 
</div> 
<div> 
    <input 
        type="button"
        id="search-item"
        value="Remove this item"
        {{action "remove_Item" this.item}} 
    /> 
</div> 
<br/> 
<div> 
    <input 
        type="button"
        id="len-list"
        value="Print Total length of list"
        {{action "print_len"}} 
    /> 
</div> 
<br/> 
<div> 
    <input 
        type="button"
        id="list-first"
        value="Print first element of list"
        {{action "print_first"}} 
    /> 
</div> 
<br/> 
<div> 
    <input 
        type="button"
        id="list-last"
        value="Print last element of list"
        {{action "print_last"}} 
    /> 
</div> 
{{outlet}}