<html>
<body>
<p>y = 5, 计算 x = y / 2, x 为:</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
var y = 5;
var x = y / 2;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>