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This article mainly shows you "how to use bind in js", the content is simple and easy to understand, and the organization is clear. I hope it can help you solve your doubts. Let Xiaobian lead you to study and learn this article "how to use bind in js".

The bind method is a new method in EcmaScript5 and is introduced on mdn as follows:

The bind() method creates a new function (called a bound function) that, when called, sets its this keyword to the value provided, and provides a given sequence of arguments before any provision when the new function is called.

Grammar:

fun.bind(thisArg[, arg1[, arg2[, …]]])

The parameter thisArg indicates that when the binding function is called, this parameter will be used as a pointer to this. This parameter is invalid when the binding function is called with the new operator.

Parameters arg1, arg2, …indicate that when the bound function is called, these parameters are passed to the bound method before arguments.

Let's start with an example:

this.name ="jack"; var demo={name:"rose",getName:function(){return this.name;}}console.log(demo.getName());//output rose where this points to demovar another=demo.getName;console.log(another())//output jack where this points to the global object//use the bind method to change this to var another2=another.bind(demo);console.log(another2());//output rose where this points to the demo object

Application of bind

You can preset initial parameters for a function:

function a(){return Array.prototype.slice.call (arguments);//Convert class array to real array}var b=a.bind(this,15,20)alert(b());/Popup 15, 20var s=b(25,30);alert(s);//Popup 15, 20, 25, 30

js bind multiple bindings are valid only the first time

var getname = function(){console.log(this.name)};var m = getname.bind({name:'q1'}).bind({name:'q2'});m();

The output is q1.

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