JavaScript Basics callback function

Simply put, the callback function: that is, the function that will be executed.

(1) Definition of callback function

function Add (X,Y,FN) {        /        * * this.x  this.y: definition        of global variable that belongs to the Add Class * / This        . x=x| | 1 ;         this. y=y| | 1 ;         if (FN) {     /* determines if there is a callback function, and some words execute the incoming function (incoming parameter)*            /FN (this. x+  This . y);        }    }

(2) Call of callback function, usually anonymous function, with return value

  Add (1,2, function (v) {//) The callback function has        a return value if(v>0) {            alert (  "result>0")        }else{            alert ( " result<0 " )        }    })

Summary: The callback function will automatically return the value, when the call will be the anonymous function as a parameter, as the formal parameters of the accepted function, at this time equivalent to become the anonymous function to perform all the rights of the agent, after execution will use the return value.

JavaScript Basics callback function