Layui implements the login interface verification code

<div class="layui-form-item">
    <div class="layui-col-xs6" >
      <input type="text" value="" placeholder="Please enter the verification code (not case sensitive)" class="input-val"> 
      <canvas id="canvas" width="100" height="30"></canvas>  
     </div>
      <div>
      <input type="button" value="Login" 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"); //Get the canvas object, the actor var context = canvas.getContext("2d"); //Get the canvas drawing environment, the actor's performance stage 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; //Get the length of the array for (var i = 0; i <= 3; i++) {
                var j = Math.floor(Math.random() * aLength); //Get a random index value var deg = Math.random() * 30 * Math.PI / 180; //Generate a random radian between 0 and 30 var txt = aCode[j]; //Get a random content show_num[i] = txt.toLowerCase();
                var x = 10 + i * 20; //x coordinate of the text on the canvasvar y = 20 + Math.random() * 8; //y coordinate of the text on the canvascontext.font = "bold 23px Microsoft YaHei";

                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++) { //Display lines on the verification code 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++) { //Show small dots on the verification code 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() { //Get a random color value 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>