AngularJS 表单验证小结
注：本文所述的表单验证即AngularJS自带的表单验证，无需引入第三方的插件
一、常用的验证特性标签
1.非空
为input加入一个required属性即可，例如：
<input type="text" required>
2.最大长度，最小长度
为input加上ng-maxlength或者ng-minlength属性，并且属性值为需要设置的长度，例如：
<input type="text" ng-minlength="5" ng-maxlength="20" />
3.邮箱
将input的type设置为email即可，例如：
<input type="email"/>
4.数字
与邮箱同理，将type设置为number<input type="number"/>
5.URL
将type设置为url
6.正则表达式
使用ng-pattern来指定正则表达式，例如：<input type="text" ng-pattern="/[a-zA-Z]/" />
还有非常多的特性，等待大家探索......
二、验证消息的展示
1.$invalid和$valid
例:<span ng-show="model.$invalid" class="text-danger">error message.</span>
表单name.字段名.$invalid 或者 表单name.字段名.$valid 中获得验证是否通过，最终来决定验证消息是否显示，如果是获取表单中所有元素是否通过验证，直接使用 表单name.$invalid 或者 表单name.$valid
$valid是通过验证时为true，不通过为false,$invalid是没有通过验证时为true,不通过为false.
2.$error
$error中会包含比较详细的错误信息，包括错误类型，错误消息，错误的字段等等~
下面是我抓取的一段整个form表单的$error信息，具体的可以参考一下angular的文档，这里我也没有去深入研究。
{"required":[{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"bookName","$options":null},{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[null],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"isbn","$options":null},{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"author","$options":null},{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"price","$options":null},{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"pressDate","$options":null},{"$validators":{},"$asyncValidators":{},"$parsers":[],"$formatters":[null],"$viewChangeListeners":[],"$untouched":true,"$touched":false,"$pristine":true,"$dirty":false,"$valid":false,"$invalid":true,"$error":{"required":true},"$name":"description","$options":null}]}
$error的用法同$valid，需要获取哪个字段的就是 表单name.字段name.$error
