菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p>点击按钮查看字符串是否以指定的子字符串开头。</p>

<button onclick="myFunction()">点我</button>

<p id="demo"></p>

<p><strong>注意:</strong> IE 11 及更早版本不支持 startsWith() 方法 。</p>
	
<script>
function myFunction() {
  var str = "Hello world, welcome to the Runoob.";
  var n = str.startsWith("world", 6);
  document.getElementById("demo").innerHTML = n;
}
</script>

</body>
</html>
              