代码示例:(标识:eg_js_variables_add_numbers)
<!DOCTYPE html>
<html>
<body>

<h1>JavaScript 变量</h1>

<p>相加 5 + 2 + 3 的结果:</p>

<p id="demo"></p>

<script>
var x = 3 + 5 + 8;
document.getElementById("demo").innerHTML = x;
</script>

</body>
</html>
运行结果: