x
 
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript 变量</h2>
<p>在本例中,x 被定义为变量。然后 x 被赋值 7:</p>
<p id="demo"></p>
<script>
var x;
x = 7;
document.getElementById("demo").innerHTML = x;
</script>
</body>
</html>