tryjsref_number_placeholder 在线代码实例

 <input type="number" id="myNumber" placeholder="Quantity">
<p>点击按钮修改 number 字段的提示信息。</p>
<button onclick="myFunction()">点我</button>
<p id="demo"></p>
<script>
function myFunction() {
    document.getElementById("myNumber").placeholder = "Amount";
}
</script>