角范围函数执行两次当它应该只运行一次？ [英] Angular scope function executed twice when it should only run once?

问题描述

演示这里

快速的问题：？在下面的code，我只调用该函数 isSpecificPage（）一次，为什么两次CONSOLE.LOG

 ＆LT; D​​IV NG隐藏=isSpecificPage（）＆GT;
  ＆LT; P＆GT;您好！＆LT; / P＆GT;
＆LT; / DIV＆GT;
 

解决方案

角把手表上的 NG-隐藏功能，使每一个消化周期可以看到，如果结果改变了（因此，如果它需要从隐藏到显示的元素或反之亦然更改）。

在观看功能评估（在 $消化），如果其中任何已从previous改变 $消化然后角知道变化会波及通过其他观看功能（也许改变的变量在另一个观看功能使用）。所以每腕表重新评估（也叫脏处理），直到没有任何的改变手表的结果。因此，通常你会看到两个通话每消化功能看，有时多个（最多10圈10-通过它放弃并报告错误说，它不能稳定）。

下面是更多关于看和消化：

  

http://docs.angularjs.org/api/ng 。$ rootScope.Scope

  
  

HTTP：// WWW。 benlesh.com/2013/08/angularjs-watch-digest-and-apply-oh-my.html

Demo here

Quick question: in the following code I only call the function isSpecificPage() once, why it console.log twice?

<div ng-hide="isSpecificPage()">
  <p>Hello!</p>
</div>

解决方案

Angular puts a watch on your ng-hide function so that every digest cycle it can see if the results changed (and thus if it needs to change from hiding to showing your element or vice-versa).

When watched functions are evaluated (during $digest) if any of them have changed from the previous $digest then Angular knows that change might ripple through to other watched functions (perhaps the changed variable is used in another watched function). So every watch is re-evaluated (also called dirty processing) until none of the watches results in a change. Thus typically you'll see 2 calls to watched functions per digest and sometimes more (up to 10- at 10 loops through it gives up and reports an error saying it can't stabilize).

Here's more on watch and digest:

http://docs.angularjs.org/api/ng.$rootScope.Scope

http://www.benlesh.com/2013/08/angularjs-watch-digest-and-apply-oh-my.html

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