How to make CAPTCHA by javascript

This article introduces the relevant knowledge of "how to make javascript CAPTCHA". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Javascript method for making CAPTCHA: [var code; _ window.onload = function creatCode () {code= ""; var codeLength = 4; var checkCode =...}].

This article operating environment: windows10 system, javascript 1.8.5, thinkpad T480 computer.

Use javascript to implement the login verification code function. Here is the specific implementation code:

Test.html

Verification code

CheckCode.js

Var code; / / globally define the length of the verification code _ window.onload = function createCode () {code = ""; var codeLength = 4ram / the length of the verification code var checkCode = document.getElementById ("code") Var random = new Array (0Phone1, 2, 4, 5, 6, 7, 8, 9, 5, 7, 8, 9, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 7, 8, 9, 5, 5, 5, 5, 6, 7, 8, 9, 7, 8, 9, 7, 8, 8, 7, 7, 8, 9, 7, 7, 8, 9, 7, 7, 8, 9, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 7, 8, 8, 7, 7, 8, 7, 8, 8, 7, 7, 8, 9, 7, 8, 9, 7, 8, 9, 7, 8, 9, 7, 8, 9, 7, 8, 'Z') / / Random number for (var I = 0; I < codeLength; iTunes +) {/ / Loop operation var index = Math.floor (Math.random () * 36); / / get the index of random number (0,35) code + = random [index]; / / add random number to code according to the index} checkCode.value = code / / assign the code value to the verification code} / / the verification code function validate () {var inputCode = document.getElementById ("input") .value.toUpperCase (); / / get the input verification code and convert it to uppercase if (inputCode.length