107 lines
2.1 KiB
Markdown
107 lines
2.1 KiB
Markdown
---
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id: bad87fee1348bd9aedf08830
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title: 给输入框添加占位符文本
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challengeType: 0
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videoUrl: 'https://scrimba.com/p/pVMPUv/cKdJDhg'
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forumTopicId: 16647
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dashedName: add-placeholder-text-to-a-text-field
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---
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# --description--
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占位符文本用户在 `input` 输入框中输入任何东西前的预定义文本。
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你可以像这样创建一个占位符：
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`<input type="text" placeholder="this is placeholder text">`
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**注意：**别忘了 `input` 元素是 "自闭和标签"，即不需要结束标签。
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# --instructions--
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把 `input` 输入框的 `placeholder` 占位符文本设置为 "cat photo URL"。
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# --hints--
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给现有的 `input` 输入框添加一个 `placeholder` 属性。
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```js
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assert($('input[placeholder]').length > 0);
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```
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设置占位符属性的值为 `cat photo URL`。
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```js
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assert(
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$('input') &&
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$('input').attr('placeholder') &&
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$('input')
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.attr('placeholder')
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.match(/cat\s+photo\s+URL/gi)
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);
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```
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`input` 元素不该有结束标签。
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```js
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assert(!code.match(/<input.*\/?>.*<\/input>/gi));
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```
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`input` 输入框的语法必须正确。
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```js
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assert($('input[type=text]').length > 0);
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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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<input type="text">
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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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<input type="text" placeholder="cat photo URL">
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</main>
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```
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