HTML5验证输入框

<input name="" id="" type="text" maxlength="11"  placeholder="用户名" required='required' autofocus="" oninput="setCustomValidity('');" oninvalid="setCustomValidity('用户名不能为空')" />

HTML5知识：

定义默认值：placeholder="用户名"  

验证不为空： required='required'   oninput="setCustomValidity('');" oninvalid="setCustomValidity('用户名不能为空')"       一定要加这个：required='required'

focus输入框：autofocus="autofocus"

验证输入字段为字母： pattern="[a-zA-Z]+"    eg:<input type="text" pattern="[a-zA-Z]+" oninvalid="setCustomValidity('Custom Message')" />