JS Realizes Random Verification Code Function

1. Verification code verification is a verification point that often appears on web pages. There are many types of verification codes. The following code only realizes a simple verification function.

 <div> 
  <input type = "text" id = "input" value="" /> 
  <input type = "button" id="code" onclick="createCode()"/> 
  <input type = "button" value = " Validation " onclick = "validate()"/> 
 </div> 

2. Add some styles casually

 #code{ 
    font-family:Arial; 
    font-style:italic; 
    font-weight:bold; 
    border:0; 
    letter-spacing:2px; 
    color:blue; 
   }

3. JS, in which I have added detailed remarks

// Settings 1 A global variable, which is convenient to save the verification code 
 var code;
 function createCode(){
  // Default first code Is an empty string 
  code = '';
  // Set the length, look at the demand here, and I set it here 4
  var codeLength = 4;
  var codeV = document.getElementById('code');
  // Set random characters 
  var random = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R', 'S','T','U','V','W','X','Y','Z');
  // Cycle codeLength  I set it up 4 Is the loop 4 Times 
  for(var i = 0; i < codeLength; i++){
   // Set the range of random numbers , This is set to 0 ~ 36
    var index = Math.floor(Math.random()*36);
    // String splicing   Will each random character   Carry out splicing 
    code += random[index]; 
  }
  // Assign the spliced string to the displayed Value
  codeV.value = code;
 }
 // The following is to judge whether or not ==  No need to explain the code of 
 function validate(){
  var oValue = document.getElementById('input').value.toUpperCase();
  if(oValue ==0){
   alert(' Please enter the verification code ');
  }else if(oValue != code){
   alert(' The verification code is incorrect, please re-enter it ');
   oValue = ' ';
   createCode();
  }else{
   window.open('http://www.baidu.com','_self');
  }
 }
 // The reason for setting this place is that every time you enter the interface display, 1 Random verification code, blank if not set 
 window.onload = function (){
  createCode();
 }

Special reference of js verification code: https://www.ofstack.com/Special/922. htm