Ember.js ArrayProxy firstObject 属性

Ember.js 是一个开源的JavaScript框架，用于开发基于Model-View-Controller (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。它被设计用于加快开发速度和提高生产力。目前，它被许多网站所使用，包括Square, Discourse, Groupon, Linked In, Live Nation, Twitch和Chipotle。

firstObject 是一个返回数组中第一个对象的属性。

语法:

Array.firstObject

参数：

Array（数组）： 这是我们想要获取其第一个元素的数组。

返回值： 数组中的第一个元素。

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，您需要先安装ember-cli。在终端中编写以下代码：

npm install ember-cli

现在，您可以通过输入以下代码来创建项目：

ember new <project-name> --lang en

启动服务器的方法是输入：

ember server

示例1： 输入以下代码以生成此示例的路由：

ember generate route first1

app/routes/first1.js

import Route from '@ember/routing/route';
 
export default class PartyRoute extends Route {
    partyItems = [
        'Oxygen',
        'Source Code',
        'Infinite',
        '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/first1.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/first1.hbs

{{page-title "firstObject"}}
<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}}

输出： 访问localhost:4200/first1以查看输出

Ember.js ArrayProxy firstObject 属性

示例2： 输入以下代码以生成本示例的路线：

ember generate route first2

app/routes/first2.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/first2.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/first2.hbs

{{page-title "firstObject"}}
<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/first2 查看输出

Ember.js ArrayProxy firstObject 属性