56 lines
1.2 KiB
Markdown
56 lines
1.2 KiB
Markdown
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---
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title: Required
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localeTitle: 需要
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---
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## 需要
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HTML required属性在input元素中用于以输入表单所需的形式输入字段。 如果用户没有填写输入字段，表单将不会提交，并且会发出一条消息，要求用户填写该字段。 `< Required>`属性适用于`<input>` ， `<select>` ， `<textarea>` 。
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例如：
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```html
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<!DOCTYPE html>
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<html>
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<head>
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<title>HTML Required Attribute</title>
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</head>
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<body>
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<form action="/">
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Text Field: <input type="text" name="textfield" required>
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<input type="submit" value="Submit">
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</form>
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</body>
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</html>
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```
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选择示例：
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```html
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<form action="/action.php">
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<select required>
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<option value="">None</option>
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<option value="volvo">Volvo</option>
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<option value="saab">Saab</option>
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<option value="mercedes">Mercedes</option>
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<option value="audi">Audi</option>
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</select>
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</form>
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```
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文本区域示例：
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```html
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<form action="/action.php">
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<textarea name="comment" required></textarea>
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<input type="submit">
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</form>
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```
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简单地添加`required`的输入元件
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#### 更多信息：
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[关于输入元素的MDN文章](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input)
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