杨校老师课堂之JavaScript定时器案例的红绿灯设计

使用JavaScript知识完成红绿灯案例

演示效果：

示例代码：

<!DOCTYPE html>
<html>
 
 
	<head>
		<meta charset="UTF-8">
		<title>红绿灯倒计时</title>
		<style>
			.box {
				width: 250px;
				height: 52px;
				padding: 15px 30px;
				border: 2px solid #ccc;
				border-radius: 16px;
				margin: 0 auto;
			}
			
			.box .count {
				width: 60px;
				color: #666;
				font-size: 280%;
				line-height: 50px;
				padding-left: 6px;
				margin-left: 5px;
				border: 1px solid #fff
			}
			
			.box div {
				margin-left: 5px;
				float: left;
				width: 50px;
				height: 50px;
				border-radius: 50px;
				border: 1px solid #666;
			}
			
			.gray {
				background-color: #eee;
			}
			
			.red {
				background-color: red;
			}
			
			.yellow {
				background-color: yellow;
			}
			
			.green {
				background-color: #26ff00;
			}
		</style>
	</head>
 
 
	<body>
		<div class="box">
			<div id="red"></div>
			<div id="yellow"></div>
			<div id="green"></div>
			<div class="count" id="count"></div>
		</div>
		<script>
			// 获取红、黄、绿灯以及倒计时的元素对象
			var lamp = {
				red: {
					obj: document.getElementById(\'red\'),
					timeout: 30,
					style: [\'red\', \'gray\', \'gray\'],
					next: \'green\'
				},
				yellow: {
					obj: document.getElementById(\'yellow\'),
					timeout: 5,
					style: [\'gray\', \'yellow\', \'gray\'],
					next: \'red\'
				},
				green: {
					obj: document.getElementById(\'green\'),
					timeout: 35,
					style: [\'gray\', \'gray\', \'green\'],
					next: \'yellow\'
				},
				changeStyle(style) {
					this.red.obj.className = style[0];
					this.yellow.obj.className = style[1];
					this.green.obj.className = style[2];
				}
			};
			var count = {
				obj: document.getElementById(\'count\'),
				change: function(num) {
					this.obj.innerHTML = (num < 10) ? (\'0\' + num) : num;
				}
			};
			var now = lamp.green;
			var timeout = now.timeout;
			lamp.changeStyle(now.style);
			count.change(timeout);
			setInterval(function() {
				if(--timeout <= 0) {
					now = lamp[now.next];
					timeout = now.timeout;
					lamp.changeStyle(now.style);
				}
				count.change(timeout);
			}, 1000);
		</script>
	</body>
 
 
</html>
　有看不懂的地方，欢迎留言提问，必将一一解答！