ng-if和ng-show/ng-hide的区别是什么

@Gajus Kuizinas and @CodeHater are correct. Here i am just giving an example. While we are working with ng-if, if the assigned value is false then the whole html elements will be removed from DOM. and if assigned value is true, then the html elements will be visible on the DOM. And the scope will be different compared to the parent scope. But in case of ng-show, it wil just show and hide the elements based on the assigned value. But it always stays in the DOM. Only the visibility changes as per the assigned value.

http://plnkr.co/edit/3G0V9ivUzzc8kpLb1OQn?p=preview

希望这个例子能帮助你理解范围。尝试给ng-show和ng-if赋假值，并在控制台中检查DOM。尝试在输入框中输入值并观察差异。

<!DOCTYPE html>

你好砰砰作响!

<input type="text" ng-model="data">
<div ng-show="true">
    <br/>ng-show=true :: <br/><input type="text" ng-model="data">
</div>
<div ng-if="true">
    <br/>ng-if=true :: <br/><input type="text" ng-model="data">
</div> 
{{data}}

2014-11-18 04:33:04

ng-if if false will remove elements from DOM. This means that all your events, directives attached to those elements will be lost. For example, ng-click to one of child elements, when ng-if evaluates to false, that element will be removed from DOM and again when it is true it is recreated. ng-show/ng-hide does not remove the elements from DOM. It uses CSS styles (.ng-hide) to hide/show elements .This way your events, directives that were attached to children will not be lost. ng-if creates a child scope while ng-show/ng-hide does not.

2016-05-27 10:37:22

事实上，ng-if指令与ng-show指令不同，它创建了自己的作用域，导致了有趣的实际差异:

angular.module('app', []).controller('ctrl', function($scope){ $scope.delete = function(array, item){ array.splice(array.indexOf(item), 1); } }) <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script> <div ng-app='app' ng-controller='ctrl'> <h4>ng-if:</h4> <ul ng-init='arr1 = [1,2,3]'> <li ng-repeat='x in arr1'> {{show}} <button ng-if='!show' ng-click='show=!show'>Delete {{show}}</button> <button ng-if='show' ng-click='delete(arr1, x)'>Yes {{show}}</button> <button ng-if='show' ng-click='show=!show'>No</button> </li> </ul> <h4>ng-show:</h4> <ul ng-init='arr2 = [1,2,3]'> <li ng-repeat='x in arr2'> {{show}} <button ng-show='!show' ng-click='show=!show'>Delete {{show}}</button> <button ng-show='show' ng-click='delete(arr2, x)'>Yes {{show}}</button> <button ng-show='show' ng-click='show=!show'>No</button> </li> </ul> <h4>ng-if with $parent:</h4> <ul ng-init='arr3 = [1,2,3]'> <li ng-repeat='item in arr3'> {{show}} <button ng-if='!show' ng-click='$parent.show=!$parent.show'>Delete {{$parent.show}}</button> <button ng-if='show' ng-click='delete(arr3, x)'>Yes {{$parent.show}}</button> <button ng-if='show' ng-click='$parent.show=!$parent.show'>No</button> </li> </ul> </div>

在第一个列表，on-click事件，显示变量，从内部/自己的作用域，被改变了，但ng-if正在观察从外部作用域同名的另一个变量，所以解决方案不工作。对于ng-show，我们只有一个show变量，这就是它工作的原因。要修复第一次尝试，我们应该通过$parent.show引用show from parent/outer scope。

2017-10-25 12:58:05

@EdSpencer是正确的。如果您有很多元素，并且使用ng-if只实例化相关的元素，则可以节省资源。 @CodeHater也有点正确，如果你要经常删除和显示一个元素，隐藏它而不是删除它可以提高性能。

我发现ng-if的主要用例是，如果内容是非法的，它允许我清晰地验证和消除元素。例如，我可以引用一个空图像名称变量，这将抛出一个错误，但如果我ng-if并检查它是否为空，这一切都很好。如果我执行ng-show，错误仍然会触发。

2014-08-14 10:40:41

@Gajus Kuizinas and @CodeHater are correct. Here i am just giving an example. While we are working with ng-if, if the assigned value is false then the whole html elements will be removed from DOM. and if assigned value is true, then the html elements will be visible on the DOM. And the scope will be different compared to the parent scope. But in case of ng-show, it wil just show and hide the elements based on the assigned value. But it always stays in the DOM. Only the visibility changes as per the assigned value.

http://plnkr.co/edit/3G0V9ivUzzc8kpLb1OQn?p=preview

希望这个例子能帮助你理解范围。尝试给ng-show和ng-if赋假值，并在控制台中检查DOM。尝试在输入框中输入值并观察差异。

<!DOCTYPE html>

你好砰砰作响!

<input type="text" ng-model="data">
<div ng-show="true">
    <br/>ng-show=true :: <br/><input type="text" ng-model="data">
</div>
<div ng-if="true">
    <br/>ng-if=true :: <br/><input type="text" ng-model="data">
</div> 
{{data}}

2014-11-18 04:33:04

ngIf通过删除或重新创建元素对DOM进行操作。

而ngShow应用css规则来隐藏/显示内容。

对于大多数情况(并非总是如此)，我将总结为，如果你需要一次检查来显示/隐藏东西，使用ng-if，如果你需要根据屏幕上的用户操作显示/隐藏东西(比如选中复选框然后显示文本框，未选中然后隐藏文本框等)，那么使用ng-show

2018-12-03 18:34:27

ng-if和ng-show/ng-hide的区别是什么

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