角度JS中双花括号和单花括号的区别? [英] Difference between double and single curly brace in angular JS?

问题描述

我是这个有角度的世界的新手，我对双花括号 {{}} 的使用有点困惑和单个大括号{}或有时不使用大括号来包含像指令中的表达式

1. ng-class={表达式}
2. 普通数据绑定如{{obj.key}}
3. ng-hide='mydata==="red"'

解决方案

{{}} - 双花括号:

{{}} 是 Angular 表达式，当您希望将内容写入 HTML 时非常方便:

{{行星名称==地球"?"是啊！我们到家了！": "诶！我们在哪儿?"}}
<!-- 带有一些指令，如 `ngSrc` --><img ng-src="http://www.example.com/gallery/{{hash}}"/><!-- 设置标题属性--><div ng-attr-title="{{celebrity.name}}">...<!-- 为您的自定义指令设置自定义属性--><div custom-directive custom-attr="{{pizza.size}}"></div>

不要在已经是表达式的地方使用这些！

例如，指令 ngClick 将引号之间的任何内容视为表达式:

<!-- 所以不要这样做！--><!-- <button ng-click="activate({{item}})">... -->

{} - 单花括号:

{} 正如我们所知，代表 JavaScript 中的对象.这里也没什么不同:

使用一些指令，如 ngClass 或 ngStyle 接受地图:

<span ng-style="{'color' : 'red'}">{{viruses.length}} 发现病毒！</span><div ng-class="{'green' : 蔬菜 == '生菜','红色' : 蔬菜 == '番茄'}">..

没有花括号:

正如已经提到的，在表达式内部时不要使用括号.很简单:

警报！所有的猴子都逃走了！

I am new to this angular world, i am bit confused with the use of double curly braces {{}} and single curly braces{} or sometime no curly brace is used to include the expression like in the directives

1. ng-class={expression}
2. normal data binding like{{obj.key}}
3. ng-hide='mydata==="red"'

解决方案

{{}} - double curly braces:

{{}} are Angular expressions and come quite handy when you wish to write stuff to HTML:

<div>
    {{planet.name == "Earth" ? "Yeah! We 're home!" : "Eh! Where 're we?"}}
</div>

<!-- with some directives like `ngSrc` -->
<img ng-src="http://www.example.com/gallery/{{hash}}"/>

<!-- set the title attribute -->
<div ng-attr-title="{{celebrity.name}}">...

<!-- set a custom attribute for your custom directive -->
<div custom-directive custom-attr="{{pizza.size}}"></div>

Don't use these at a place that is already an expression!

For instance, the directive ngClick treats anything written in between the quotes as an expression:

<!-- so dont do this! -->
<!-- <button ng-click="activate({{item}})">... -->  

{} - single curly braces:

{} as we know stand for objects in JavaScript. Here, too, nothing different:

<div ng-init="distanceWalked = {mon:2, tue:2.5, wed:0.8, thu:3, fri:1.5, 
sat:2, sun:3}">

With some directives like ngClass or ngStyle that accept map:

<span ng-style="{'color' : 'red'}">{{viruses.length}} viruses found!</span>

<div ng-class="{'green' : vegetable == 'lettuce', 
'red' : vegetable == 'tomato'}">..

no curly braces:

As already mentioned just go braceless when inside expressions. Quite simple:

<div ng-if="zoo.enclosure.inmatesCount == 0">
    Alarm! All the monkeys have escaped!
</div>

 

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