179 lines
5.4 KiB
Markdown
179 lines
5.4 KiB
Markdown
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---
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title: Form Validation
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localeTitle: 表格验证
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---
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## 表格验证
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在客户端输入所有必要数据然后按下“提交”按钮后，通常用于在服务器上进行的表单验证。如果数据 客户输入的内容不正确或只是丢失，服务器必须将所有数据发送回客户端并请求表单 重新提交正确的信息。这真是一个漫长的过程，曾经给服务器带来了很多负担。
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JavaScript提供了一种在将客户端计算机上的数据发送到Web服务器之前验证其数据的方法。表单验证通常执行两次 功能：
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### 基本验证
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首先，必须检查表单以确保填写所有必填字段。它只需要循环遍历表单中的每个字段， 检查数据。
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### 数据格式验证
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其次，必须检查输入的数据的正确形式和值。您的代码必须包含适当的逻辑来测试数据的正确性。
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#### 例：
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```html
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<html>
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<head>
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<title>Form Validation</title>
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<script type="text/javascript">
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<!--
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// Form validation code will come here.
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//-->
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</script>
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</head>
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<body>
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<form action="/cgi-bin/test.cgi" name="myForm" onsubmit="return(validate());">
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<table cellspacing="2" cellpadding="2" border="1">
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<tr>
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<td align="right">Name</td>
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<td><input type="text" name="Name" /></td>
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</tr>
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<tr>
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<td align="right">EMail</td>
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<td><input type="text" name="EMail" /></td>
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</tr>
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<tr>
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<td align="right">Zip Code</td>
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<td><input type="text" name="Zip" /></td>
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</tr>
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<tr>
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<td align="right">Country</td>
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<td>
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<select name="Country">
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<option value="-1" selected>[choose yours]</option>
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<option value="1">USA</option>
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<option value="2">UK</option>
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<option value="3">INDIA</option>
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</select>
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</td>
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</tr>
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<tr>
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<td align="right"></td>
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<td><input type="submit" value="Submit" /></td>
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</tr>
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</table>
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</form>
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</body>
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</html>
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```
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#### 产量
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[在这里了解一下](https://liveweave.com/LP9eOP)
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### 基本表格验证
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首先让我们看看如何进行基本表单验证。在上面的表单中，我们调用validate（）来在onsubmit事件发生时验证数据。该 以下代码显示了此`validate()`函数的实现。
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```html
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<script type="text/javascript">
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// Form validation code will come here.
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function validate()
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{
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if( document.myForm.Name.value == "" )
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{
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alert( "Please provide your name!" );
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document.myForm.Name.focus() ;
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return false;
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}
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if( document.myForm.EMail.value == "" )
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{
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alert( "Please provide your Email!" );
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document.myForm.EMail.focus() ;
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return false;
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}
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if( document.myForm.Zip.value == "" ||
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isNaN( document.myForm.Zip.value ) ||
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document.myForm.Zip.value.length != 5 )
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{
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alert( "Please provide a zip in the format #####." );
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document.myForm.Zip.focus() ;
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return false;
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}
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if( document.myForm.Country.value == "-1" )
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{
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alert( "Please provide your country!" );
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return false;
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}
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return( true );
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}
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</script>
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```
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#### 产量
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[在这里了解一下](https://liveweave.com/pCPTnP)
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### 数据格式验证
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现在我们将看到如何在将输入的表单数据提交到Web服务器之前验证它们。
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以下示例显示如何验证输入的电子邮件地址。电子邮件地址必须至少包含“@”符号和点（。）。此外，'@'必须 不是电子邮件地址的第一个字符，最后一个点必须至少是“@”符号后面的一个字符。
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#### 例：
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```html
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<script type="text/javascript">
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function validateEmail()
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{
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var emailID = document.myForm.EMail.value;
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atpos = emailID.indexOf("@");
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dotpos = emailID.lastIndexOf(".");
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if (atpos < 1 || ( dotpos - atpos < 2 ))
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{
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alert("Please enter correct email ID")
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document.myForm.EMail.focus() ;
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return false;
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}
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return( true );
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}
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</script>
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```
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#### 产量
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[在这里了解一下](https://liveweave.com/nznVs6)
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### HTML5表单约束
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`<input>`一些常用HTML5约束是`type`属性（例如`type="password"` ）， `maxlength` ， `required`和`disabled` 。少了 常用的约束是采用JavaScript正则表达式的`pattern` attrinute。
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### 验证库
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验证库的示例包括：
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* [Validate.js](http://rickharrison.github.com/validate.js/)
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* [验证](http://bassistance.de/jquery-plugins/jquery-plugin-validation/)
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* [Valid8](http://unwrongest.com/projects/valid8/)
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### 更多信息
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* [表格数据验证| MDN](https://developer.mozilla.org/en-US/docs/Learn/HTML/Forms/Form_validation)
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* [约束验证| MDN](https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/HTML5/Constraint_validation)
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* [Tutorialspoint](https://www.tutorialspoint.com/javascript/javascript_form_validations.htm)
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