AS3：为什么“this”会在函数内部改变它指的是什么？

Question

我的代码

for each(var enemy in RhythmGame.npcs) { 
    if(this.hitTestObject(enemy)) { 
     enemy.step(distance, axis, origin); 
     enemy.damage(power); 
    } 
} 

正常工作，直到我把它放在一个函数

separate(); 
function separate():void { 
    for each(var enemy in RhythmGame.npcs) { 
     if(this.hitTestObject(enemy)) { 
      enemy.step(distance, axis, origin); 
      enemy.damage(power); 
     } 
    } 
} 

，然后我得到的错误

TypeError: Error #1006: hitTestObject is not a function.

我发现this指的是[object global]当它在函数中而不是类实例时它应该是。为什么会发生？我在这里不了解范围如何工作？

Answer 1

I've found that this is referring to [object global] when it's in the function rather than the class instance it should be. Why would this happen? What don't I understand here about how scope works?

这是预期的行为，如果你的函数是一个关闭而不是方法。我猜你所发布的代码本身包含在一个函数或一个类方法中，可能稍后会被称为回调函数或其他东西。

从the docs on function scope：

The main difference between a function closure and a bound method is that the value of the this keyword in a bound method always refers to the instance to which it was originally attached, whereas in a function closure the value of the this keyword can change.