javascript函数内的this关键字

在javascript函数内的this指的是谁？一句话： The word "this" within a function refers to the object calling that function.

举例子，如下javascript代码

Javascript函数Ball()内引用了this关键字，有三个cases验证这个值

Case 1: 调用Ball()函数的对象是o

  "this" point to object "o", so this is an Object object, and this.constructor is "function Object()", and variable "v" is attached to object "o".

Case 2: 调用Ball()函数的对象是b
  "this" point to object "b", so this is an Ball object, and this.constructor is "function Ball()", and variable "v" is attached to object "b".
  Notice: this case works like:
  var b = new Object();
  b.construct = Ball;
  b.construct("222");  // executes b.Ball("222")

Case 3: 调用Ball()函数的对象是全局对象window
  "this" point to object root object, i.e,. window object in browser, so this is an Window object, and this.constructor is "function Window()", and variable "v" is attached to object window, i.e,. "v" becomes a global variable.