How to implement four-digit random verification code in javascript

Javascript method to implement four-digit random verification code: first create a random number through "function random(max,min){...}"; then create it through "function code(){...}" Random four-digit verification code; finally call the verification code function.

The operating environment of this article: windows7 system, javascript version 1.8.5, DELL G3 computer

How does javascript implement a four-digit random verification code?

JS implements 4-digit random verification code

Write a 4-digit random number that is case-insensitive and contains numbers through random numbers.

CSS style

p{
 width: 60px;
 height: 20px;
 display: inline-block;
 letter-spacing: 3px;
 border: 1px solid red;
}
#p{
 height: 20px;
 margin-bottom: 10px;
}
#btn,p:hover{
 cursor: default;
}
button{
 display: block;
}

Main part

<p id="box">
验证码
 <input type="text" id="int" />
 <p id="p"></p>
 <p id="p"></p>
 <button id="btn">提交</button>
</p>

JS part

//随机数
function random(max,min){
 return Math.round(Math.random()*(max-min)+min);
}
//随机4位验证码
function code(){
 //将数字、小写字母及大写字母输入
 var str="1234567890qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM";
 //给一个空字符串
 var res='';
 //循环4次，得到4个字符
 for(var i=0;i<4;i++){
 //将得到的结果给字符串，调用随机函数，0最小数，62表示数字加字母的总数
 res+=str[random(0,62)];
 }
 p.innerHTML=res;
}
code(); //调用验证码函数
p.onclick=code; //点击也可以刷新验证码
//验证验证码
btn.onclick=function(){
 var int=document.getElementById("int").value;//获取用户输入的值
 var p=document.getElementById("p").innerText;//获取验证码
 //判断用户输入与验证码的大写一致(不分大小写)
 if(int.toUpperCase()==p.toUpperCase()){
 p.innerHTML="验证码正确";
 }else{
 p.innerHTML="验证码错误";
 }
}

Achievement result

Summary

Math.round(): Rounding
Math.random(): Random number
toUpperCase(): Convert the string to uppercase

Recommended study: "javascript Advanced Tutorial"

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