请注意，现在发生在我身上的一件事: Ng-show通过css隐藏内容，是的，但它导致了奇怪的小故障在div的应该是按钮。

我有一个底部有两个按钮的卡，根据实际状态，一个与第三个交换，示例编辑按钮与新条目。使用ng-show=false来隐藏左边的按钮(首先出现在文件中)，下面的按钮的右边框出现在卡片外面。 Ng-if通过完全不包括代码来修复这个问题。 (只是在这里检查是否有一些隐藏的惊喜使用ng-if而不是ng-show)

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.

@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。

也许有趣的一点是，两者的优先级不同。

据我所知，ng-if指令是所有Angular指令中优先级最高(如果不是最高的话)的指令之一。这意味着:它将在所有其他低优先级的指令之前运行。事实上，它首先运行，意味着有效地，在任何内部指令被处理之前，元素被删除。至少，我是这么认为的。

I observerd and used this in the UI I'm building for my current customer. The entire UI is quite heavily packed, and it had ng-show and ng-hide all over it. Not to go into too much detail, but I built a generic component, which could be managed using JSON config, so I had to do some switching inside the template. There is an ng-repeat present, and inside the ng-repeat, a table is shown, which has a lot of ng-shows, ng-hides and even ng-switches present. They wanted to show at least 50 repeats in the list, which would result in more or less 1500-2000 directives to be resolved. I checked the code, and the Java backend + custom JS on the front would take about 150ms to process the data, and then Angular would chew some 2-3 seconds on it, before displaying. The customer did not complain, but I was appalled :-)

In my search, I stumbled across the ng-if directive. Now, maybe it's best to point out that at the point of conceiving this UI, there was no ng-if available. Because the ng-show and ng-hide had functions in them, which returned booleans, I could easily replace them all with ng-if. By doing so, all inner directives seemed to be no longer evaluated. That meant that I dropped back to about a third of all directives being evaluated, and thus, the UI speeded up to about 500ms - 1 sec loading time. (I have no way to determine exact seconds)

注意:指令没有被评估的事实，是对下面发生的事情的一个有根据的猜测。

所以，在我看来:如果你需要元素出现在页面上(即:检查元素，或其他)，但只是被隐藏，请使用ng-show/ng-hide。在所有其他情况下，使用ng-if。

关于ng-if和ng-show需要注意的一件重要的事情是，当使用表单控件时，最好使用ng-if，因为它完全从dom中删除了元素。

这个区别很重要，因为如果你创建了一个required="true"的输入字段，然后设置ng-show="false"来隐藏它，当用户试图提交表单时，Chrome会抛出以下错误:

An invalid form control with name='' is not focusable.

原因是输入字段是存在的，它是必需的，但由于它是隐藏的Chrome不能关注它。这可能会破坏您的代码，因为此错误会停止脚本执行。所以要小心!

请注意，现在发生在我身上的一件事: Ng-show通过css隐藏内容，是的，但它导致了奇怪的小故障在div的应该是按钮。

我有一个底部有两个按钮的卡，根据实际状态，一个与第三个交换，示例编辑按钮与新条目。使用ng-show=false来隐藏左边的按钮(首先出现在文件中)，下面的按钮的右边框出现在卡片外面。 Ng-if通过完全不包括代码来修复这个问题。 (只是在这里检查是否有一些隐藏的惊喜使用ng-if而不是ng-show)