index.html

<!DOCTYPE html>
<html>
<head>
<meta http-eqiuv="content-type" content="text/html;charset=utf-8"/>
<link rel="stylesheet" href="style.css" type="text/css"/>
<!--script type="text/javascript" src="4.js"/-->
</head>
<body>
<div id="nihao">
<canvas id="mom" style="background:#111"></canvas>
  <script type="text/javascript">
    window.onload = function(){
//获取画布对象
        var canvas = document.getElementById("mom");
//获取画布的上下文
        var context =canvas.getContext("2d");
//获取浏览器屏幕的宽度和高度
        var W = window.innerWidth;
        var H = window.innerHeight;
//设置canvas的宽度和高度
        canvas.width = W;
        canvas.height = H;
//每个文字的字体大小
        var fontSize = 16;
//计算列
        var colunms = Math.floor(W /fontSize);
//记录每列文字的y轴坐标
        var drops = [];
//给每一个文字初始化一个起始点的位置
for(var i=0;i<colunms;i++){
            drops.push(0);
        }
//运动的文字
        var str ="asd86 asdaas87766s67a 78ad7s78sa";
//4:fillText(str,x,y);原理就是去更改y的坐标位置
//绘画的函数
        function draw(){
            context.fillStyle = "rgba(0,0,0,0.05)";
            context.fillRect(0,0,W,H);
//给字体设置样式
            context.font = "700 "+fontSize+"px  微软雅黑";
//给字体添加颜色
            context.fillStyle ="#00cc33";//可以rgb,hsl, 标准色，十六进制颜色
//写入画布中
for(var i=0;i<colunms;i++){
                var index = Math.floor(Math.random() * str.length);
                var x = i*fontSize;
                var y = drops[i] *fontSize;
                context.fillText(str[index],x,y);
//如果要改变时间，肯定就是改变每次他的起点
if(y >= canvas.height && Math.random() > 0.99){
                    drops[i] = 0;
                }
                drops[i]++;
            }
        };
        function randColor(){
            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+")";
        }
        draw();
        setInterval(draw,30);
    };
</script>
</div>
</body>
</html>