​x
 
<!DOCTYPE html>
<html>
<body>
​
<h3>如何访问 H2 元素的演示</h3>
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<h2 id="myHeading">This is a h2 element.</h2>
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<p>单击按钮将 h2 元素的颜色设置为红色。</p>
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<button onclick="myFunction()">试一试</button>
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<script>
function myFunction() {
  var x = document.getElementById("myHeading");
  x.style.color = "red";
}
</script>
​
</body>
</html>
​
​