Share with you a code that generates verification code and verifies it
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><title>JS Generate Verification Code</title><style type="text/css">.code {background-image: url(code.jpg);font-family: Arial;font-style: italic;color: Red;border: 0;padding: 2px 3px;letter-spacing: 3px;font-weight: bolder;}.unchanged {border: 0;}</style><script language="javascript" type="text/javascript"> var code; //Define verification code function createCode() { code = ""; var codeLength = 6;//Length of verification code var checkCode = document.getElementById("checkCode"); var selectChar = 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');//All candidates can also use the Chinese for (var i = 0; i < codeLength; i++) { var charIndex = Math.floor(Math.random() * 36); code += selectChar[charIndex]; } //alert(code); if (checkCode) { checkCode.className = "code"; checkCode.value = code; }} function validate() { var inputCode = document.getElementById("input1").value; if (inputCode.length <= 0) { alert("Please enter the verification code! "); } else if (inputCode != code) { alert("Verification code input error!"); createCode();//Refresh the verification code} else { alert("^-^ OK"); }}</script></head><body onload="createCode()"><form action="#"> <input type="text" id="input1" /> <input type="text" onclick="createCode()" readonly="readonly" id="checkCode" /><br /> <input id="Button1" onclick="validate();" type="button" value="OK" /></form></body></html>As we all know, js is client-side, so is it meaningful to do all verification on the client? Or is it necessary to generate the verification code from the server safe? Is the verification code generated by the front-end safe?
The verification code is dynamic, but it must be recognized by the client and returned the correct value before it can be verified normally. This is a process problem. If you are from js, it is to verify at the client, which basically means there is nothing the same! ! ! It is best to generate server, verify client, confirm server, and browse normally. This process is foolproof
Therefore, this article is just a technical discussion, and should not be used in actual production projects