How to put error message inside Placeholder

Question

I have found this Jsfiddle http://jsfiddle.net/HkEuf/2650/ which allow entering only numbers in input field. Now I want to put inside input field Placeholder which will also be error message (look at Jsfiddle).

Number : <input type="text" name="quantity" id="quantity" placeholder="Test" />

And for error message is:

<span id="errmsg"></span>

Now I whant to do this: First you see input field with placeholder "Test". So if you put numbers, placeholder deletes, and you see only numbers that you enter. But If you put non-digit chars (letters), placeholder changes into error message id="errmsg".

这可能吗？

Answer 1

添加这个

 $("#quantity").attr("placeholder","errmsg");

小提琴： 演示