<form>

用户名:<input type="text" id="usrname"><br>

密码:<input type="password" id="pwd">

</form>

<p>单击下面的按钮禁用上面的密码字段</p>

<button onclick="disableElement()">禁用密码字段</button>

<script>

function disableElement(){

    document.getElementById("pwd").disabled=true;

}

</script>

​