​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>单击按钮循环一段代码五次。</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var x = "", i;
  for (i=0; i<5; i++) {
    x = x + "数字是：" + i + "<br>";
  }
  document.getElementById("demo").innerHTML = x;
}
</script>
​
</body>
</html>
​