​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>我的第一段 JavaScript</h1>
​
<p id="demo">JavaScript 可以更改 HTML 元素的样式。</p>
​
<script>
function myFunction() {
  document.getElementById("demo").style.fontSize = "25px"; 
  document.getElementById("demo").style.color = "red";
  document.getElementById("demo").style.backgroundColor = "yellow";        
}
</script>
​
<button type="button" onclick="myFunction()">点击我！</button>
​
</body>
</html>
​