四位纯数字验证码

四位随机验证码
function random(){
var a = parseInt(Math.random()*10);
var b = parseInt(Math.random()*10);
var c = parseInt(Math.random()*10);
var d = parseInt(Math.random()*10);
return (""+a+b+c+d)
}
console.log(random());
documengt.write(random());
alert(random());

方法二

function random(a,b){
return Math.round(Math.random()*(a-b)+b);
}

function randomStr(){
var str ="";
for(var i=0;i<4;i++){
str += random(0,9);
}
return str;
}
console.log(randonStr());

来源：https://blog.csdn.net/Xdrea/article/details/102748631