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<!DOCTYPE html>
<html>
<body>
​
<h1>JavaScript Prompt</h1>
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<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
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<script>
function myFunction() {
  var txt;
  var person = prompt("请输入您的名字：", "哈利波特");
  if (person == null || person == "") {
    txt = "用户取消输入";
  } else {
    txt = "你好，" + person + "！今天过得好吗？";
  }
  document.getElementById("demo").innerHTML = txt;
}
</script>
​
</body>
</html>
​