问题描述
在code是简单的：
<!doctype html>
<html ng-app="plunker" >
<head>
<meta charset="utf-8">
<title>AngularJS Plunker</title>
<script>document.write("<base href=\"" + document.location + "\" />");</script>
<link rel="stylesheet" href="style.css">
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.4/angular.js"></script>
</head>
<body ng-controller="MainCtrl">
Hello {{name()}}!
</body>
</html>
<script>
var app = angular.module('plunker', []);
app.controller('MainCtrl', function($scope) {
$scope.name= function() {
console.log("---name---:" + new Date());
return "Freewind";
};
});
</script>
您可以看到有一个名称函数，我们调用它在体内只有一次。但在控制台，它打印的两倍 ---名字--- ：
You can see there is a name function and we invoke it in the body only one time. But in the console, it prints twice of ---name---::
---name---:Wed Feb 20 2013 14:38:12 GMT+0800 (中国标准时间)
---name---:Wed Feb 20 2013 14:38:12 GMT+0800 (中国标准时间)
您可以看到现场演示在这里：<一href=\"http://plnkr.co/edit/tb8RpnBJZaJ73V73QISC?p=$p$pview\">http://plnkr.co/edit/tb8RpnBJZaJ73V73QISC?p=$p$pview
You can see a live demo here: http://plnkr.co/edit/tb8RpnBJZaJ73V73QISC?p=preview
为什么功能名称（）被调用两次？
Why the function name() has been invoked two times?
推荐答案
在AngularJS，什么都用双花括号是的是被评估的>至少一次。
In AngularJS, anything wrapped in double curly braces is an expression that gets evaluated at least once during the digest cycle.
AngularJS通过持续运行的消化周期，直到一切都没有改变的作品。这就是它如何确保认为是先进的日期。既然你调用的函数，它的运行一次得到一个值，然后第二次看到，一切都没有改变。在下一个周期中消化，它至少会再次运行。
AngularJS works by running the digest cycle continuously until nothing has changed. That's how it ensures the view is up-to-date. Since you called a function, it's running it once to get a value and then a second time to see that nothing has changed. On the next digest cycle, it will run at least once again.
这通常是一个好主意，只调用幂等方法（如名称）从模板因为这个原因。
It's generally a good idea to only call idempotent methods (like name) from the template for this very reason.
这篇关于为什么angularjs将调用函数'名称（）`两次？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！