<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 字符串方法</h1>
<p>padStart() 方法用另一段字符串来填充字符串：</p>
<p id="demo"></p>
<script>
let text = "5";
document.getElementById("demo").innerHTML = text.padStart(4,0);
</script>
</body>
</html>