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js+canvas实现验证码功能

2020-11-27 来源：爱go旅游网

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;
}

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);
})