AngularJS摘要循环多久运行一次？ [英] How often does the AngularJS digest loop run?

问题描述

在讨论AngularJS的优点时，双向数据绑定通常被称为Angular对其他JS框架的主要优点。 深入挖掘，文档表明此过程是通过肮脏检查而不是通过事件驱动的措施来完成。首先，通过在每个周期内通过在后台进行方法触发，似乎在循环中检查所有的 $ watch es。然而，进一步阅读，似乎摘要循环实际上是由 rootScope.digest（）触发的，而这又由 $触发。 ，这又是由一个事件（！）引发的，例如通过 ng-click 调用的onClick事件。

When discussing the merits of AngularJS, two-way data binding is often touted as a major benefit of Angular over other JS frameworks. Digging deeper, the documentation suggests this process is done through dirty-checking rather than through event-driven measures. At first, it seems that the digest-loop works by having a method fire off in the background at periodic intervals, checking all the $watches during each cycle. However, reading further, it seems that the digest-loop is actually triggered by rootScope.digest(), which in turn is triggered by $.apply, which is in turn triggered by an event(!), such as an onClick event called through ng-click.

但是，怎么可能？我以为Angular 不使用变更听众。那么摘要循环是如何运作的呢？ Angular会自动在内部启动摘要循环，还是由事件触发摘要循环？如果摘要循环自动运行，运行的频率如何？

But, how can this be? I thought Angular doesn't use change listeners. So how does the digest-loop really operate? Does Angular automatically kick-off the digest-loop internally, or is the digest-loop triggered by events? If the digest-loop is run automatically, how often does it run?

一些澄清点：

• 我不是询问手动绑定到更改时如何运行digest-loop。在这种情况下，如果要强制执行摘要循环，可以通过调用 $。apply（）


• m也不会询问摘要循环响应用户事件的频率。例如，如果ng-model在输入框上，Angular将在用户开始输入时启动摘要循环。令人困惑的部分是为了知道一个用户正在打字，Angular不会在某个地方使用一个基于事件的


• 我已经知道有每个摘要循环最多10个循环。我的问题不在于每个摘要循环的循环次数，而是每秒钟运行的摘要循环的次数。


• 奖金问题：如何使用摘要循环涉及JavaScript事件循环？ JS事件循环是否在后台定期运行？消息循环与事件循环相同，但只能在角色环境中？这些完全不同的想法？

• I'm not asking about how the digest-loop runs when manually binding to changes. In this case, if you want to force a digest loop, you can do so by calling $.apply()
• I'm also not asking about how often digest loop runs in response to user events. For example, if ng-model is on an input box, Angular will kick-off a digest loop when a user starts typing. The confusing part is that in order to know a user was typing, doesn't Angular use an event-based onKeyUp somewhere?
• I already know that there is a limit of 10 cycles max per digest-loop. My question is less about the number of cycles per digest-loop, but rather the number of digest-loops that run, say, per second.
• Bonus questions: How does the digest-loop relate to the JavaScript event-loop? Does the JS event loop run periodically in the background? Is the digest-loop the same thing as the event loop, but only in the "Angular Context"? Are these totally different ideas?

推荐答案

角色摘要被触发 - 它们不会发生在

Angular digests are triggered - they don't happen through polling.

代码执行后，角色触发摘要。

Code executes, after code is done, angular triggers a digest.

示例：

 element.on('click', function() {
     $scope.$apply(function() { 
         // do some code here, after this, $digest cycle will be triggered
     });
 });

Angular还会在编译/链接阶段后触发$ digest：

Angular will also trigger a $digest after the compile/link phase:

Compile > Link > Digest

以及触发了多少个摘要循环？这取决于范围变量的稳定程度。通常需要至少2个周期来确定。

And as to how many digest cycles are triggered? It depends on how soon the scope variables stabalise. Usually it takes at least 2 cycles to determine that.

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