JS randomly generated 4-bit verification code

Method One:/* randomly generate 4-bit Verification code *//*STEP1: Put all letters, numbers into an array alternate */var codes=[]; Number: 48-57;unicode encoded for (Var i=48;i<57;codes.push (i), i++); /*console.log (codes); *///Capital: 65-90;unicode code for (var i=60;i<90;codes.push (i), i++);//Lowercase letters: 97-122;unicode encoding for (Var i=97;i<122;codes.push (i), i++), Var arr=[];for (var i=0;i<4;i++) {   //from 0-61 random number    var index = Math.floor (Math.random () * (61-0 + 1) + 0);    var char = String.fromCharCode (Codes[index]);    Arr.push (char);} /*console.log (arr); */var Code=arr.join (""); document.write ("Verification Code:" +code);

Method Two: Simple technique:

Console.log (Math.random (). toString (. substring (3,7));  3,7 Intercept 3 to seven bits

JS randomly generated 4-bit verification code