<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>随机显示颜色</title>
<style>
#div1{
100px;
height: 100px;
}
</style>
</head>
<body onload="change()">
<div id="div1"></div>
</body>
<script>
function change(){
var i=Math.random()*10;
var div1=document.getElementById("div1");
if(0<i<4){
div1.style.backgroundColor="red";
}
if(4<=i&&i<7){
div1.style.backgroundColor="yellow";
}
if(7<=i&&i<10){
div1.style.backgroundColor="green";
}
}
</script>
</html>