layui实现登陆界面验证码

<div class="layui-form-item">    <div class="layui-col-xs6" >      <input type="text" value="" placeholder="请输入验证码（不区分大小写）" class="input-val">       <canvas id="canvas" width="100" height="30"></canvas>       </div>      <div>      <input type="button" value="登录"  class="layui-btn layui-btn-fluid" lay-submit lay-filter="login">       </div>         </div>

var show_num=[];  $(function()  {   draw(show_num);   $("#canvas").on('click',function()   {  draw(show_num);         })        }); 

function draw(show_num) {            var canvas_width = $('#canvas').width();            var canvas_height = $('#canvas').height();            var canvas = document.getElementById("canvas");//获取到canvas的对象，演员            var context = canvas.getContext("2d");//获取到canvas画图的环境，演员表演的舞台            canvas.width = canvas_width;            canvas.height = canvas_height;            var sCode = "A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0";            var aCode = sCode.split(",");            var aLength = aCode.length;//获取到数组的长度            for (var i = 0; i <= 3; i++) {                var j = Math.floor(Math.random() * aLength);//获取到随机的索引值                var deg = Math.random() * 30 * Math.PI / 180;//产生0~30之间的随机弧度                var txt = aCode[j];//得到随机的一个内容                show_num[i] = txt.toLowerCase();                var x = 10 + i * 20;//文字在canvas上的x坐标                var y = 20 + Math.random() * 8;//文字在canvas上的y坐标                context.font = "bold 23px 微软雅黑";                context.translate(x, y);                context.rotate(deg);                context.fillStyle = randomColor();                context.fillText(txt, 0, 0);                context.rotate(-deg);                context.translate(-x, -y);            }            for (var i = 0; i <= 5; i++) { //验证码上显示线条                context.strokeStyle = randomColor();                context.beginPath();                context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height);                context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height);                context.stroke();            }            for (var i = 0; i <= 30; i++) { //验证码上显示小点                context.strokeStyle = randomColor();                context.beginPath();                var x = Math.random() * canvas_width;                var y = Math.random() * canvas_height;                context.moveTo(x, y);                context.lineTo(x + 1, y + 1);                context.stroke();            }        }        function randomColor() {//得到随机的颜色值            var r = Math.floor(Math.random() * 256);            var g = Math.floor(Math.random() * 256);            var b = Math.floor(Math.random() * 256);            return "rgb(" + r + "," + g + "," + b + ")";        }

<style>        .code {            width: 100%;            margin: 0 auto;        }        .input-val {            width: 63%;            background: #ffffff;            height: 2.8rem;            padding: 0 2%;            border-radius: 5px;            border: none;            border: 1px solid rgba(0,0,0,.2);            font-size: 0.9rem;        }        #canvas {            float: right;            display: inline-block;            border: 1px solid #ccc;            border-radius: 5px;            cursor: pointer;        }</style>