Three ways of writing callback function in JS

Three ways to type a callback function:

1. Call by pointer

2. Call by anonymous function

3, the definition and execution at the same time

   　　　　   //to invoke by a pointer            functionMath (num1,num2,callback) {returncallback (NUM1, num2); }            functionAA (num1,num2) {returnNUM1 +num2; }            functionBB (num1,num2) {returnNUM1-num2; } console.log (Math (2,1,AA));//3Console.log (Math (2,1,BB));//1                                    //by anonymous function calls (essentially the same as in the first way)            functionMath (num1,num2,callback) {returncallback (NUM1,NUM2); } console.log (Math (2, 1,function(num1,num2) {returnNUM1 +num2; })            ); //3                                    //definition and execution at the same time (self-executing)(function(num) {console.log (num); } )(1);//1

the function of the callback function : You can write the tool method for external use (the argument is logically processed, and then return the result directly to the callback function is OK)

// processing the input parameter, outputting the result to the callback function for external use        function Parsestr (param,callback) {            var result = param + ' very handsome ';            Callback (result);        }        Parsestr (' Xu Wenxiang ',function(result) {            console.log (result);   // Xu Wenxiang very handsome        })

　

Three ways of writing callback function in JS