<!DOCTYPE html>
<html>
<body>
<h2>JavaScript 提升</h2>
<p>使用 <b>var</b>，您可以在声明变量之前使用它：</p>
<p id="demo"></p>
<script>
carName = "Audi";
document.getElementById("demo").innerHTML = carName;
var carName;
</script>
</body>
</html>