canvas_07 炫彩小球
效果图：
1 <!DOCTYPE html> 2 <html lang="en"> 3 4 <head> 5 <meta charset="UTF-8"> 6 <meta http-equiv="X-UA-Compatible" content="IE=edge"> 7 <meta name="viewport" content="width=device-width, initial-scale=1.0"> 8 <title>Canvas</title> 9 <style> 10 * { 11 margin: 0; 12 padding: 0; 13 } 14 </style> 15 </head> 16 17 <body> 18 <canvas id="canvas"></canvas> 19 20 <script> 21 var canvas = document.querySelector("#canvas"); 22 var ctx = canvas.getContext("2d"); 23 // -6是滚动条 24 var w = document.documentElement.clientWidth - 6; 25 var h = document.documentElement.clientHeight - 6; 26 canvas.width = w; 27 canvas.height = h; 28 29 function randNum(num) { 30 return Math.random() * num; 31 } 32 33 function drawCricle(x, y, r, color) { 34 ctx.beginPath(); 35 ctx.arc(x, y, r, 0, Math.PI * 2); 36 ctx.fillStyle = color || "#000"; 37 ctx.fill(); 38 } 39 40 function Ball(x, y) { 41 this.x = x; 42 this.y = y; 43 this.r = 60; 44 this.color = "rgb(" + parseInt(Math.random() * 255) + 45 "," + parseInt(Math.random() * 255) + 46 "," + parseInt(Math.random() * 255) + ")"; 47 } 48 49 Ball.prototype.show = function() { 50 this.r--; 51 drawCricle(this.x, this.y, this.r, this.color); 52 } 53 54 function animation() { 55 var ballArr = []; 56 window.onmousemove = function(e) { 57 var ball = new Ball(e.x, e.y); 58 ballArr.push(ball); 59 ball.show(); 60 } 61 62 setInterval(() => { 63 ctx.clearRect(0, 0, w, h); 64 for (var i = 0; i < ballArr.length; i++) { 65 var ball = ballArr[i]; 66 if (ball.r <= 0) { 67 ballArr.splice(i, 1); 68 } else { 69 ball.show(); 70 } 71 } 72 }, 10); 73 } 74 75 animation(); 76 </script> 77 </body> 78 79 </html>