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！
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