A re-introduction to JavaScript(developer.mozilla.org)

  >>> class foo():
  ...   def test(this, x):
  ...     print this, x
  ... 
  >>> x = foo()
  >>> x
  <__main__.foo instance at 0xb71928ac>
  >>> x.test(1)
  <__main__.foo instance at 0xb71928ac> 1
  >>> y = foo.test
  >>> y(1)
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  TypeError: unbound method test() must be called with foo instance as first argument (got int instance instead)
  >>> y(x,1)
  <__main__.foo instance at 0xb71928ac> 1

  function foo() { }
  foo.prototype.test = function(x) {
    console.log(this, x);
  }
  var x = new foo();
  x.test(1); // prints VM1061:4 foo {test: function} 1
  var y = x.test;
  y(1); // prints VM1061:4 Window {top: Window, window: Window, …} 1

  var that = this;