<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script>
var arr = ["北京" , "上海" , "南京"];
var scc = arr.push("湖北" , "西安");
alert(arr);
alert(scc);
</script>
</head>
<body>
</body>
</html>
假如不把arr.push赋给 scc的话，那么alert（arr）= "北京" , "上海" , "南京""湖北" , "西安"；
为什么把arr.push赋给scc后，alert（scc）就变成了阿拉伯数字？
