JS learning bind function

definition:

bind() Method creates a new function, in  bind() is called, this new function  this is specified as  bind() the first parameter, and the remaining arguments as parameters of the new function for use during calls.

usage:

bind() The simplest use is to create a function, no matter how called, this function has the same  this value.

    <script>
            var  name='hhh';
            function demo(){
                console.log('demo.name',this.name);
            }
            var a={
                name:"linjianbin",
            }
        var demo2=    demo.bind(a);
        demo();///hhh
        demo2();//linjianbin
        </script>

2.bind() Another simplest usage is to have a function preset initial parameters. As long as these parameters (if any) as a  bind() parameter written in  this the back. When the binding function is called, these parameters will be inserted into the starting position of the objective function parameter list, the parameters passed to the binding functions will follow them. ,

        var demo= function(){
            return arguments;
        }
        var demo2=demo.bind(demo,23);
            console.log(demo2(1,2,3,4,5));//23,1,2,3,4,5
        

3. By default, the use  window.setTimeout() , the this key point to  window (or  global) objects. When the class method requires  this point to instances of the class, you may need to explicitly  this bind to the callback function, you do not lose the instance reference.

    <script>
        function LateBloomer() {
          this.petalCount = 10 + 1;
        }
        
        // 在 1 秒钟后声明 bloom
        LateBloomer.prototype.bloom = function() {
          window.setTimeout(this.declare.bind(this), 1000);
        };
        
        LateBloomer.prototype.declare = function() {
          console.log('I am a beautiful flower with ' +
            this.petalCount + ' petals!');
        };
        
        var Flower = new new LateBloomer (); 
        flower.bloom ();   // a second after call 'declare' Method
             
    </ script>