The Call/apply/bind in JS

<script>        var obj = {            A:1        }            var a = 2;                 function Test (a)        {            alert (a);            Alert (this. a);        }         </script>

1.test (3);

Results: "3", "2";

Explanation: Argument 3 is passed to parameter a, and parameter a inside the function overrides global variable A, so the first is 3, and this in the function is the window object, so THIS.A is 2

2.test.call (thisobject,param1,param2 ...);

Thisobject: Change the point of this in the test function;

Param: Pass a parameter to the test function as a string

　　Test.call (NULL);

Results: "Undefined", "2";

Explanation: When test (a) is executed, no arguments are passed, a is undefined, because the pass thisobject is null, when the test function is executed, the browser points to the Window object when the THISOBEJCT is not pointed, so the second popup is 2. The same test.call (undefined), the result ibid.

3.test.call (null,3);

Results: "3", "2";

4.test.call (obj);

Results: "Undefined", "1";

5.test.call (obj,3);

Results: "3", "1";

6.test.apply (Thisobject,[param1,param2 .....));

In addition to passing parameters to the function in the form of an array, the other and call (Thisobject,param1,param2 ...);

7.test.bind (Thisobject,param1,param2 ...)

Thisobject: Change this to point to

Param: Parameters

This method returns the function object that this change points to, and gets the arguments

var ss = Test.bind (NULL);

SS ();

Result: "Undefined", "2"

var ss = Test.bind (obj);

SS ();

Results: "Undefined", "1";

var ss = Test.bind (obj,3);

SS ();

Results: "3", "2";

When a function has more than one parameter:

function Test (a,b,c) {    alert (a+ ":" +b+ ":" +c);}         var ss = Test.bind (obj,3); SS (4,5,6);

The result: 3,4,5 is not 4,5,6, because in Bind, the 3 is assigned to a, at the SS (4,5,6), 6 is not assigned to C;

The value saved in arguments is 3,4,5,6;

The Call/apply/bind in JS