​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>JavaScript 字符串方法</h1>
​
<p>把字符串转换为大写：</p>
​
<button onclick="myFunction()">试一试</button>
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<p id="demo">Hello World!</p>
​
<script>
function myFunction() {
  var text = document.getElementById("demo").innerHTML;
  document.getElementById("demo").innerHTML = text.toUpperCase();
}
</script>
​
</body>
</html>
​