<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<script>
(function () {
var a = 1;
console.log(a);
})(); // 这个分号必须存在！！！！
(function () {
var a = 2;
console.log(a);
})();
</script>
</body>
</html>
