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How to use html to achieve the effect of meteor shower (code)

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Aug 15, 2018 pm 04:57 PM

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The content of this article is about how to use HTML to achieve the effect of meteor shower (code). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

<!doctype html>
<html>
	<head>
		<meta charset="GB2312" />
		<title>流星雨</title>
		<meta name="keywords" content="关键词，关键字">
		<meta name="description" content="描述信息">
		<style>
			body {
				margin: 0;
				overflow: hidden;
			}
		</style>
	</head>
 
	<body>
 
		<!--
			<canvas>画布 画板 画画的本子
		-->
		<canvas width=400 height=400 style="background:#000000;" id="canvas"></canvas>
 
		<!--
			javascript
			画笔
		--> 
		<script>
					
			//获取画板
			//doccument 当前文档
			//getElement 获取一个标签
			//ById 通过Id名称的方式
			//var 声明一片空间
			//var canvas 声明一片空间的名字叫做canvas
			var canvas = document.getElementById("canvas");
			//获取画板权限 上下文
			var ctx = canvas.getContext("2d");
			//让画板的大小等于屏幕的大小
			/*
				思路：
					1.获取屏幕对象
					2.获取屏幕的尺寸
					3.屏幕的尺寸赋值给画板
			*/
			//获取屏幕对象
			var s = window.screen;
			//获取屏幕的宽度和高度
			var w = s.width;
			var h = s.height;
			//设置画板的大小
			canvas.width = w;
			canvas.height = h;
 
			//设置文字大小 
			var fontSize = 14;
			//计算一行有多少个文字 取整数 向下取整
			var clos = Math.floor(w/fontSize);
			//思考每一个字的坐标
			//创建数组把clos 个 0 （y坐标存储起来）
			var drops = [];
			var str = "qwertyuiopasdfghjklzxcvbnm";
			//往数组里面添加 clos 个 0
			for(var i = 0;i<clos;i++) {
				drops.push(0);
			}
 
			//绘制文字
			function drawString() {
				//给矩形设置填充色
				ctx.fillStyle="rgba(0,0,0,0.05)"
				//绘制一个矩形
				ctx.fillRect(0,0,w,h);
 
				//添加文字样式
				ctx.font = "600 "+fontSize+"px 微软雅黑";
				//设置文字颜色
				ctx.fillStyle = "#ff2d2d";
 
				for(var i = 0;i<clos;i++) {
					//x坐标
					var x = i*fontSize;
					//y坐标
					var y = drops[i]*fontSize;
					//设置绘制文字
					ctx.fillText(str[Math.floor(Math.random()*str.length)],x,y);
					if(y>h&&Math.random()>0.99){
						drops[i] = 0;
					}
					drops[i]++;
				}
					
			}
			//定义一个定时器，每隔30毫秒执行一次
			setInterval(drawString,30);
		</script>
	</body>
</html>

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