91 lines
2.1 KiB
Markdown
91 lines
2.1 KiB
Markdown
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---
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id: 587d781e367417b2b2512acb
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title: 絕對定位的參照物是元素的父元素
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challengeType: 0
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videoUrl: 'https://scrimba.com/c/cyLJ7c3'
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forumTopicId: 301060
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dashedName: lock-an-element-to-its-parent-with-absolute-positioning
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---
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# --description--
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接下來要介紹 CSS `position` 屬性的取值選項 `absolute`，它的含義是相對於其包含塊定位。 和 `relative` 定位不一樣，絕對定位會將元素從當前的文檔流裏面移除，周圍的元素會忽略它。 這樣我們就可以用 CSS 的 top、bottom、left、right 屬性來調整元素的位置。
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絕對定位比較特殊的一點是元素的定位參照於最近的 *positioned* 祖先元素。 如果它的父元素沒有添加定位規則（默認是 `position: relative;`），瀏覽器會繼續尋找直到默認的 `body` 標籤。
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# --instructions--
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通過設置 `position` 屬性值爲 `absolute`，將 `#searchbar` 元素固定到它的父元素 `section` 的右上角。 即設定其 `top` 和 `right` 爲 50 像素。
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# --hints--
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`#searchbar` 元素的 `position` 屬性值應爲 `absolute`。
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```js
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assert($('#searchbar').css('position') == 'absolute');
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```
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`#searchbar` 元素的 `top` 屬性值應爲 50px。
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```js
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assert($('#searchbar').css('top') == '50px');
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```
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`#searchbar` 元素的 `right` 屬性值應爲 50px。
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```js
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assert($('#searchbar').css('right') == '50px');
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```
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# --seed--
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## --seed-contents--
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```html
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<style>
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#searchbar {
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}
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section {
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position: relative;
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}
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</style>
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<body>
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<h1>Welcome!</h1>
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<section>
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<form id="searchbar">
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<label for="search">Search:</label>
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<input type="search" id="search" name="search">
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<input type="submit" name="submit" value="Go!">
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</form>
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</section>
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</body>
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```
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# --solutions--
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```html
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<style>
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#searchbar {
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position: absolute;
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top: 50px;
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right: 50px;
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}
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section {
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position: relative;
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}
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</style>
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<body>
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<h1>Welcome!</h1>
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<section>
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<form id="searchbar">
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<label for="search">Search:</label>
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<input type="search" id="search" name="search">
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<input type="submit" name="submit" value="Go!">
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</form>
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</section>
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</body>
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```
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