87 lines
2.2 KiB
Markdown
87 lines
2.2 KiB
Markdown
---
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id: bad87fee1348bd9aedc08830
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title: 给表单添加一个必填字段
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challengeType: 0
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videoUrl: 'https://scrimba.com/p/pVMPUv/cMd4EcQ'
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forumTopicId: 18360
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dashedName: use-html5-to-require-a-field
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---
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# --description--
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当你设计表单时，你可以指定某些字段为必填项（required），只有当用户填写了该字段后，才可以提交表单。
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如果你想把文本输入框设置为必填项，在 `input` 元素中加上 `required` 属性就可以了，例如：`<input type="text" required>`
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# --instructions--
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请给 `input` 元素加上 `required` 属性，这样用户就必须先在输入框里填入内容，然后才可以提交表单。
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然后尝试在不输入任何文本的情况下提交表单， 看看 HTML5 表单是如何通知你这个字段是必填的。
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# --hints--
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`input` 元素应有 `required` 属性。
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```js
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assert($('input').prop('required'));
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```
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# --seed--
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## --seed-contents--
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```html
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<h2>CatPhotoApp</h2>
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<main>
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<p>Click here to view more <a href="#">cat photos</a>.</p>
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<a href="#"><img src="https://bit.ly/fcc-relaxing-cat" alt="A cute orange cat lying on its back."></a>
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<p>Things cats love:</p>
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<ul>
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<li>cat nip</li>
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<li>laser pointers</li>
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<li>lasagna</li>
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</ul>
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<p>Top 3 things cats hate:</p>
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<ol>
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<li>flea treatment</li>
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<li>thunder</li>
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<li>other cats</li>
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</ol>
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<form action="https://freecatphotoapp.com/submit-cat-photo">
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<input type="text" placeholder="cat photo URL">
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<button type="submit">Submit</button>
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</form>
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</main>
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```
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# --solutions--
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```html
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<h2>CatPhotoApp</h2>
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<main>
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<p>Click here to view more <a href="#">cat photos</a>.</p>
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<a href="#"><img src="https://bit.ly/fcc-relaxing-cat" alt="A cute orange cat lying on its back."></a>
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<p>Things cats love:</p>
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<ul>
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<li>cat nip</li>
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<li>laser pointers</li>
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<li>lasagna</li>
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</ul>
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<p>Top 3 things cats hate:</p>
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<ol>
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<li>flea treatment</li>
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<li>thunder</li>
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<li>other cats</li>
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</ol>
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<form action="https://freecatphotoapp.com/submit-cat-photo">
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<input type="text" required placeholder="cat photo URL">
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<button type="submit">Submit</button>
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</form>
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</main>
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```
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