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---
id: bad87eee1348bd9aede07836
title: 設置元素的 id
challengeType: 0
videoUrl: 'https://scrimba.com/c/cN6MEc2'
forumTopicId: 18279
dashedName: set-the-id-of-an-element
---
# --description--
除了 class 屬性,每一個 HTML 元素都有一個 `id` 屬性。
使用 `id` 有幾個好處:你可以通過 `id` 選擇器來改變單個元素的樣式。在稍後的課程中,你還會了解到如何在 JavaScript 裏面用它來選擇和操作元素。
根據規範,`id` 屬性應是唯一的。 儘管瀏覽器並非必須執行這條規範,但這是廣泛認可的最佳實踐。 因此,請不要給多個元素設置相同的 `id` 。
設置 `h2` 元素的 id 爲 `cat-photo-app` 的代碼如下:
```html
< h2 id = "cat-photo-app" >
```
# --instructions--
設置`form` 元素的 id 爲`cat-photo-form` 。
# --hints--
`form` 元素的 id 應爲 `cat-photo-form` 。
```js
assert($('form').attr('id') === 'cat-photo-form');
```
# --seed--
## --seed-contents--
```html
< link href = "https://fonts.googleapis.com/css?family=Lobster" rel = "stylesheet" type = "text/css" >
< style >
.red-text {
color: red;
}
h2 {
font-family: Lobster, monospace;
}
p {
font-size: 16px;
font-family: monospace;
}
.thick-green-border {
border-color: green;
border-width: 10px;
border-style: solid;
border-radius: 50%;
}
.smaller-image {
width: 100px;
}
.silver-background {
background-color: silver;
}
< / style >
< h2 class = "red-text" > CatPhotoApp< / h2 >
< main >
< 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://cdn.freecodecamp.org/curriculum/cat-photo-app/relaxing-cat.jpg" alt = "A cute orange cat lying on its back." > < / a >
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< div class = "silver-background" >
< p > Things cats love:< / p >
< ul >
< li > cat nip< / li >
< li > laser pointers< / li >
< li > lasagna< / li >
< / ul >
< p > Top 3 things cats hate:< / p >
< ol >
< li > flea treatment< / li >
< li > thunder< / li >
< li > other cats< / li >
< / ol >
< / div >
< form action = "https://freecatphotoapp.com/submit-cat-photo" >
< label > < input type = "radio" name = "indoor-outdoor" checked > Indoor< / label >
< label > < input type = "radio" name = "indoor-outdoor" > Outdoor< / label > < br >
< label > < input type = "checkbox" name = "personality" checked > Loving< / label >
< label > < input type = "checkbox" name = "personality" > Lazy< / label >
< label > < input type = "checkbox" name = "personality" > Energetic< / label > < br >
< input type = "text" placeholder = "cat photo URL" required >
< button type = "submit" > Submit< / button >
< / form >
< / main >
```
# --solutions--
```html
< link href = "https://fonts.googleapis.com/css?family=Lobster" rel = "stylesheet" type = "text/css" >
< style >
.red-text {
color: red;
}
h2 {
font-family: Lobster, monospace;
}
p {
font-size: 16px;
font-family: monospace;
}
.thick-green-border {
border-color: green;
border-width: 10px;
border-style: solid;
border-radius: 50%;
}
.smaller-image {
width: 100px;
}
.silver-background {
background-color: silver;
}
< / style >
< h2 class = "red-text" > CatPhotoApp< / h2 >
< main >
< 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://cdn.freecodecamp.org/curriculum/cat-photo-app/relaxing-cat.jpg" alt = "A cute orange cat lying on its back." > < / a >
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< div class = "silver-background" >
< p > Things cats love:< / p >
< ul >
< li > cat nip< / li >
< li > laser pointers< / li >
< li > lasagna< / li >
< / ul >
< p > Top 3 things cats hate:< / p >
< ol >
< li > flea treatment< / li >
< li > thunder< / li >
< li > other cats< / li >
< / ol >
< / div >
< form action = "https://freecatphotoapp.com/submit-cat-photo" id = "cat-photo-form" >
< label > < input type = "radio" name = "indoor-outdoor" checked > Indoor< / label >
< label > < input type = "radio" name = "indoor-outdoor" > Outdoor< / label > < br >
< label > < input type = "checkbox" name = "personality" checked > Loving< / label >
< label > < input type = "checkbox" name = "personality" > Lazy< / label >
< label > < input type = "checkbox" name = "personality" > Energetic< / label > < br >
< input type = "text" placeholder = "cat photo URL" required >
< button type = "submit" > Submit< / button >
< / form >
< / main >
```