js无法在移动设备上运行

Question

我有一个简单的表单在网络上工作但是当谈到移动设备时，它不起作用。

function validateForm() {

    var full_name = document.getElementById('full_name').value;

    if (full_name == '') {
        alert("Please enter your full name.");
        return false;
    }

}


<form method="post" id="event-form" onsubmit="return validateForm();">
    <input type="text" name="full_name" id="full_name"   >
    <input type="submit" name="roles_reminder" value="submit" class="rolessubmit" id="rolessubmit">
</form>

演示

http://jsfiddle.net/squidraj/yx5Mb/6/