Javascript - 验证，仅限数字

I'm trying to get my login form to only validate if only numbers were inputted. I can it to work if the input is only digits, but when i type any characters after a number, it will still validate etc. 12akf will work. 1am will work. How can i get past this?

部分登录

<form name="myForm">
    <label for="firstname">Age: </label>
    <input name="num" type="text" id="username" size="1">
    <input type="submit" value="Login" onclick="return validateForm()">

function validateForm()
{

    var z = document.forms["myForm"]["num"].value;
    if(!z.match(/^d+/))
        {
        alert("Please only enter numeric characters only for your Age! (Allowed input:0-9)")
        }
}

推荐答案

匹配 /^d+$/.$ 表示行尾"，因此在初始运行数字之后的任何非数字字符都会导致匹配失败.