小编给大家分享一下js+canvas如何实现验证码功能，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
刚刚开始接触canvas，写个验证码小功能练练手，实现效果图如下：
主要代码如下:
html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> <link rel="stylesheet" href="index.css" rel="external nofollow" > </head> <body> <div class="wrapper"> <div class="inputBox"> <input type="text" class = 'inputCaptcha' placeholder = "请输入验证码"> <span class="captchaIcon"></span> </div> <p class="errorText"></p> <div class="canvasBox"> <div class="imageBox"> <canvas width =300 height=80 id = 'canvasCaptcha'></canvas> <input type="button" class='refresh'> </div> </div> <button class="captchaSubmit">submit</button> </div> <script src='./jquery.js'></script> <script src = './index.js'></script> </body> </html>
css
* { margin: 0; padding: 0; } .wrapper { width: 345px; border: 1px solid #ccc; border-radius: 10px; padding: 20px 10px; margin: 30px 30px; } .inputBox { width: 345px; margin: 0 auto 10px; position: relative; } .inputBox .inputCaptcha { display: inline-block; height: 50px; width: 86%; text-indent: 1em; border: 1px solid #ddd; border-radius: 5px; } .inputBox .captchaIcon { display: none; position: absolute; top: 50%; right: 0px; margin-top: -16px; width: 32px; height: 32px; background-size: 100% 100%; } .errorText { width: 345px; margin: 0 auto; font-size: 12px; color: red; display: none; } .canvasBox { width: 345px; margin: 10px auto; position: relative; } #canvasCaptcha { border-radius: 10px; } .canvasBox .refresh { width: 34px; height: 34px; position: absolute; right: 0px; top: 50%; margin-top: -17px; border: 0; border-radius: 6px; background-image: url('./images/update.png'); background-size: cover; } .captchaSubmit { padding: 10px 20px; background-color: #62b900; border: 0; font-size: 20px; border-radius: 5px; color: #fff; }js
var arr = [0,1,2,3,4,5,6,7,8,9]; for(var i = 65;i < 122;i++){ if(i>90&&i<97){ continue; } arr.push(String.fromCharCode(i)); } //每个验证码可能出现的字母或数字(区分大小写) var len = arr.length; //验证码的长度 var canvasStr,value; //验证码值 function createCanvas(){ canvasStr = ''; value = ''; for(var i =0 ;i < 6;i++){ var a = arr[Math.floor(Math.random()*len)]; canvasStr += a+' '; value += a; } //canvas var oCanvas = document.getElementById('canvasCaptcha'); var ctx = oCanvas.getContext('2d'); var w = oCanvas.width; var h = oCanvas.height; var oImg = new Image(); oImg.src = './images/bg.jpg'; oImg.onload = function(){ var pattern = ctx.createPattern(oImg,'repeat'); ctx.fillStyle = pattern; ctx.fillRect(0,0,w,h); ctx.fillStyle = '#ccc'; ctx.textAlign = 'center'; ctx.font = '46px Roboto Slab'; ctx.setTransform(1,-0.12,0.2,1,0,12); ctx.fillText(canvasStr,w/2,60); } } createCanvas(); //验证输入的验证码与图中验证码时候相等 function captcha(e){ if(e == value){ return true; } else{ return false; } } //点击提交按钮时的结果 function showResult(){ var inputValue = $('.inputCaptcha').val(); if(inputValue == '' ||inputValue == null || inputValue == 'undefined'){ $('.errorText').css({display:'inline-block'}).html('验证码不能为空,请重新输入!'); $('.captchaIcon').css({display:'inline-block',backgroundImage:"url('./images/false.png')"}); }else{ var flag = captcha(inputValue); if(!flag){ $('.errorText').css({display:'inline-block'}).html('验证码错误,请重新输入!'); $('.captchaIcon').css({display:'inline-block',backgroundImage:"url('./images/false.png')"}); }else{ $('.captchaIcon').css({display:'inline-block',backgroundImage:"url('./images/true.png')"}); } } } $('.captchaSubmit').click(showResult);//提交 $('.refresh').click(createCanvas);//刷新 //点击input框 $('.inputCaptcha').focus(function(){ $('.errorText').add($('.captchaIcon')).fadeOut(100); })以上是“js+canvas如何实现验证码功能”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注亿速云行业资讯频道！
免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
