js+canvas实现验证码功能

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);
})

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。