2018-10-10 22:03:03 +00:00
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---
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id: bad87dee1348bd9aede07836
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2020-12-16 07:37:30 +00:00
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title: 使用 id 属性来设定元素的样式
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2018-10-10 22:03:03 +00:00
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challengeType: 0
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2019-12-13 05:47:57 +00:00
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videoUrl: 'https://scrimba.com/c/cakyZfL'
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forumTopicId: 18339
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2021-01-13 02:31:00 +00:00
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dashedName: use-an-id-attribute-to-style-an-element
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2021-01-08 19:20:48 +00:00
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通过 `id` 属性,你可以做一些很酷的事情。比如像 class 一样,你可以使用 CSS 来设置他们的样式。
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2020-12-16 07:37:30 +00:00
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2021-01-08 19:20:48 +00:00
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不过,`id` 不可以重复,它只能作用于一个元素上。同时,在 CSS 里,`id` 的优先级高于 `class`。如果一个元素同时应用了 `class` 和 `id`,且两者设置的样式有冲突,会优先应用 `id` 中所设置的样式。
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2020-12-16 07:37:30 +00:00
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2021-01-08 19:20:48 +00:00
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选择 `id` 为 `cat-photo-element` 的元素,并设置它的背景样式为 `green`,可以在 `style` 标签里这样写:
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2019-12-13 05:47:57 +00:00
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```css
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#cat-photo-element {
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background-color: green;
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}
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```
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2021-01-08 19:20:48 +00:00
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注意在 `style` 标签里,声明 class 的时候必须在名字前插入 `.` 符号。同样,在声明 id 的时候,也必须在名字前插入 `#` 符号。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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请将 id 为 `cat-photo-form` 的 `form` 表单的背景颜色设置为 `green`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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`form` 元素的 id 应为 `cat-photo-form`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('form').attr('id') === 'cat-photo-form');
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2018-10-10 22:03:03 +00:00
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```
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2021-01-08 19:20:48 +00:00
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`form` 元素应含有 `background-color` CSS 属性且其属性值应为 `green`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('#cat-photo-form').css('background-color') === 'rgb(0, 128, 0)');
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```
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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确保 `form` 元素的 `id` 设置正确。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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code.match(/<form.*cat-photo-form.*>/gi) &&
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code.match(/<form.*cat-photo-form.*>/gi).length > 0
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);
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```
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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不要在 `form` 元素上添加其他 `class` 属性或者 `style` 行内样式。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(!code.match(/<form.*style.*>/gi) && !code.match(/<form.*class.*>/gi));
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2018-10-10 22:03:03 +00:00
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```
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2019-12-13 05:47:57 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --seed-contents--
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```html
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<link href="https://fonts.googleapis.com/css?family=Lobster" rel="stylesheet" type="text/css">
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<style>
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.red-text {
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color: red;
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}
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h2 {
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font-family: Lobster, monospace;
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}
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p {
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font-size: 16px;
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font-family: monospace;
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}
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.thick-green-border {
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border-color: green;
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border-width: 10px;
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border-style: solid;
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border-radius: 50%;
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}
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.smaller-image {
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width: 100px;
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}
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.silver-background {
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background-color: silver;
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}
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</style>
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<h2 class="red-text">CatPhotoApp</h2>
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<main>
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<p class="red-text">Click here to view more <a href="#">cat photos</a>.</p>
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<a href="#"><img class="smaller-image thick-green-border" src="https://bit.ly/fcc-relaxing-cat" alt="A cute orange cat lying on its back."></a>
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<div class="silver-background">
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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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</div>
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<form action="https://freecatphotoapp.com/submit-cat-photo" id="cat-photo-form">
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<label><input type="radio" name="indoor-outdoor" checked> Indoor</label>
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<label><input type="radio" name="indoor-outdoor"> Outdoor</label><br>
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<label><input type="checkbox" name="personality" checked> Loving</label>
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<label><input type="checkbox" name="personality"> Lazy</label>
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<label><input type="checkbox" name="personality"> Energetic</label><br>
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<input type="text" placeholder="cat photo URL" required>
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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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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```html
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<link href="https://fonts.googleapis.com/css?family=Lobster" rel="stylesheet" type="text/css">
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<style>
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.red-text {
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color: red;
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}
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h2 {
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font-family: Lobster, monospace;
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}
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p {
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font-size: 16px;
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font-family: monospace;
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}
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.thick-green-border {
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border-color: green;
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border-width: 10px;
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border-style: solid;
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border-radius: 50%;
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}
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.smaller-image {
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width: 100px;
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}
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.silver-background {
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background-color: silver;
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}
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#cat-photo-form {
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background-color: green;
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}
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</style>
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<h2 class="red-text">CatPhotoApp</h2>
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<main>
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<p class="red-text">Click here to view more <a href="#">cat photos</a>.</p>
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<a href="#"><img class="smaller-image thick-green-border" src="https://bit.ly/fcc-relaxing-cat" alt="A cute orange cat lying on its back."></a>
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<div class="silver-background">
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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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</div>
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<form action="https://freecatphotoapp.com/submit-cat-photo" id="cat-photo-form">
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<label><input type="radio" name="indoor-outdoor" checked> Indoor</label>
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<label><input type="radio" name="indoor-outdoor"> Outdoor</label><br>
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<label><input type="checkbox" name="personality" checked> Loving</label>
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<label><input type="checkbox" name="personality"> Lazy</label>
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<label><input type="checkbox" name="personality"> Energetic</label><br>
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<input type="text" placeholder="cat photo URL" required>
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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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