​x
 
<!DOCTYPE html>
<html>
<body>
​
密码：<input type="password" id="myPsw" placeholder="密码 ..">
​
<p>单击该按钮可更改密码字段的占位符文本。</p>
​
<button onclick="myFunction()">试一试</button>
​
<script>
function myFunction() {
  document.getElementById("myPsw").placeholder = "输入您的密码";
}
</script>
​
</body>
</html>
​