“未捕获的类型错误：非法调用”在Chrome中

问题描述

当我使用 requestAnimationFrame 做一些原生支持的动画时，使用下面的代码：

  var support = {
 animationFrame：window.requestAnimationFrame || 
 window.mozRequestAnimationFrame || 
 window.webkitRequestAnimationFrame || 
 window.msRequestAnimationFrame || 
 window.oRequestAnimationFrame 
}; 
 
 support.animationFrame（function（）{}）; //错误
 
 support.animationFrame.call（window，function（）{}）; // right 
  

直接调用 support.animationFrame 会给... ...
$ b

在Chrome中。为什么？

解决方案

在您的代码中，您将自定义方法分配给自定义对象的属性。
当您调用 support.animationFrame（function（）{}）时，它会在当前对象（即支持）的上下文中执行。为了使本地的requestAnimationFrame函数正常工作，它必须在窗口的上下文中执行。

这里的用法是 support.animationFrame.call（window，function（）{}）; 。 还有警报：

  var myObj = {
 myAlert：alert //将本地警报复制到对象
}; 
 
 myObj.myAlert（'这是一个提醒'）; //非法
 myObj.myAlert.call（窗口，'这是一个提醒'）; //在窗口的上下文中执行
  

另一个选项是使用，它是ES5标准的一部分，可用于所有现代浏览器。

  var _raf = window.requestAnimationFrame || 
 window.mozRequestAnimationFrame || 
 window.webkitRequestAnimationFrame || 
 window.msRequestAnimationFrame || 
 window.oRequestAnimationFrame; 
 
 var support = {
 animationFrame：_raf？ _raf.bind（window）：null 
}; 
  

When I use requestAnimationFrame to do some native supported animation with below code:

var support = {
    animationFrame: window.requestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        window.oRequestAnimationFrame
};

support.animationFrame(function() {}); //error

support.animationFrame.call(window, function() {}); //right

Directly calling the support.animationFrame will give...

in Chrome. Why?

解决方案

In your code you are assigning a native method to a property of custom object.When you call support.animationFrame(function () {}) , it is executed in the context of current object (ie support). For the native requestAnimationFrame function to work properly, it must be executed in the context of window.

So the correct usage here is support.animationFrame.call(window, function() {});.

The same happens with alert too:

var myObj = {
  myAlert : alert //copying native alert to an object
};

myObj.myAlert('this is an alert'); //is illegal
myObj.myAlert.call(window, 'this is an alert'); // executing in context of window

Another option is to use Function.prototype.bind() which is part of ES5 standard and available in all modern browsers.

var _raf = window.requestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        window.oRequestAnimationFrame;

var support = {
   animationFrame: _raf ? _raf.bind(window) : null
};

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