Usage of arguments.callee

argument Is the internal object of the function , Contains all the parameters of the incoming function ,arguments.callee Represents the function name , Used for recursive calls , Prevent tight coupling between function execution and function name , It also works well for anonymous functions that don't have a function name . Examples are as follows ：

function factorial(num){
    
      if(num<=1){
    
          return 1;
      }else{
    
          return num*arguments.callee(num-1);  //arguments.callee representative factorial
      }
}
var trueFactorial = factorial;
factorial = function(){
    
	  return 0;
}
alert(trueFactorial(5)); // The result is 120, because js No overload for function in , So if you use the function name when calling recursively , Then execute the last function with this function name , Return 0
alert(factorial(5));// The result is 0

Recursion of anonymous functions ：

var num = (function(num){
    
      if(num<=1){
    
          return 1;
      }else{
    
          return num*arguments.callee(num-1);
      }
 })(5);
  alert(num); // The result is 120

Traffic light asynchronous output

function showRed(fn1, fn2){
    
    var f = arguments.callee; // The function itself 
    //arguments.callee  The context execution environment in which this function is executed , Point to the object that called him 
    setTimeout(function(){
    
        console.log(" A red light ");
        fn1(fn2, f);
    }, 2000);   
}

function showYellow(fn1, fn2){
    
    var f = arguments.callee;
    setTimeout(function(){
    
        console.log(" Yellow light ");
        fn1(fn2, f);
    }, 1000);
    
}

function showGreen(fn1, fn2){
    
    var f = arguments.callee;
    setTimeout(function(){
    
        console.log(" A green light ");
        fn1(fn2, f);
    }, 3000);
}

showRed(showYellow, showGreen);