红绿灯变换（定时器应用）

[zlluGitHub]

• 定时器应用：setInterval(function(){ }, time )

    <script>
    //鼠标经过颜色改变
    function show1() {
        var qw =document.getElementById("box1")
        qw.style.background = "wheat";
    }
    function back1() {
        var qw =document.getElementById("box1")
        qw.style.background = "pink";
    }

    //定时器红绿灯
    var n=setInterval(function(){
        var dom=document.getElementById('box2');
        var clr=dom.style.background;
        if(clr=='red'){
        	dom.style.background='green';
        }
        else{
          dom.style.background='red';
      }
    },500)
    //定时器红绿黄灯
    var n=setInterval(function(){
        qiehuan();
    },1500)
    var qiehuan=function(){
    	var dom=document.getElementById('box3');
    	var clr=dom.style.background;
    	dom.style.background='yellow';
    	setTimeout(function(){
    		if(clr=='red'){
    			dom.style.background='green';
    		}
    		else{
    			dom.style.background='red'
    		}
    	},500);
    }
    </script>

• 文件地址：定时器红绿灯