JavaScript method--bind ()

Bind method, as the name implies, is the meaning of binding, in the end how to bind then how to use it, the following is to say I understand this method.

Grammar

Fun.bind (This,arg1,arg2,...)

The bind () method creates a new function called a binding function, which is called by the fun method in the This environment

The method can pass in two parameters, the first parameter as this, the second and later arguments as the function parameters call

Instance

1. Create a binding function

1  This. A = 1;2 varmodule = {3A:2,4Geta:function() {5     return  This. A; 6     }7 };8Module.geta ();//29 Ten varGetA1 =Module.geta; One //The Geta is called externally, at which point this points to the global object AGetA1 ();//1 -  - //then bind the GetA1 method to the module environment. the varGetA2 =Geta1.bind (module); -GetA2 ();

As can be seen from the above example, the reason for creating a binding function is that when we invoke certain functions to be called in a particular environment, we are going to put the function in a specific environment, that is, bind the function to a specific desired environment using bind.

2. Let the function have preset parameters

Use the bind () method to have the default initial parameters for the function, which will be the first, and the arguments passed to the binding function will follow them.

1 functionlist () {2     //let the class array arguments the method that owns the array slice, this function realizes the simple to convert the class array to the group3     returnArray.prototype.slice.call (arguments);4 }5 6List (n/a);//[A]7 8 //bind a preset parameter to list 49 varList1 = List.bind (undefined,4);Ten  OneList1 ();//[4] A  -List1 (a);//[4,1,2,3]

Use of 3.setTimeout

Normally, this will point to the global object when calling settimeout, but we need to point to an instance of the class when using the method of the class, so to put this, bind the callback function to facilitate the use of the instance

1 functionFun1 () {2    This. Name = 1;3  }4Fun1.prototype.fun2 =function() {5Window.settimeout ( This. Fun3.bind ( This), 1000);6  }7FUN1.PROTOTYPE.FUN3 =function(){8Console.log (' Name: ' + This. name);//name:19 }Ten varFun =NewFun1 (); OneFun.fun2 ();

4. Quick Method--converting an array of classes into arrays

The first method is to use the Apply method

1 function fun1 () {2     var slice = Array.prototype.slice; 3     return slice.apply (arguments); 4 }56 fun1 (n/a); // [A]

The second approach is to use the call method with the Bind method

function fun2 () {    var unboundslice = Array.prototype.slice;     // bind the call method of the function to the array slice method, and then pass the parameter    to the call method var slice = Function.prototype.call.bind (unboundslice);     return Slice (arguments);} Fun2 (a); // [A]

There are still some difficult areas to understand about the Bind method, so be careful.

I hope you will correct me ~

JavaScript method--bind ()