Understanding the use of callback functions in JavaScript

The first thing to understand is the function object, in JavaScript, function and array object,number as an object, so function can also be like a normal object can be passed as a parameter of another function;

function parentf (callback) {//callback can define the name arbitrarily, it is only a parameter, and it is not possible to determine the type of the callback (Number,object,function is not OK)

var a=1;

var b=2;  Console.log ("parent"); Return callback (A, b);

}

function Childf (A, b) {Console.log ("child"); return a+b;

}

Window.onload=function () {

var result= parentf (CHILDF);  Console.log (result); }

Output Result:

Parent

Child

3

The above is a simple callback function.

　

Understanding the use of callback functions in JavaScript