128 lines
2.9 KiB
Markdown
128 lines
2.9 KiB
Markdown
---
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id: 587d78a8367417b2b2512ae7
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title: 使用關鍵字更改動畫定時器
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challengeType: 0
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videoUrl: 'https://scrimba.com/c/cJKvwCM'
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forumTopicId: 301045
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dashedName: change-animation-timing-with-keywords
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---
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# --description--
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在 CSS 動畫裏，`animation-timing-function` 用來定義動畫的速度曲線。 速度曲線決定了動畫從一套 CSS 樣式變爲另一套所用的時間。 如果要描述的動畫是一輛車在指定時間內（`animation-duration`）從 A 運動到 B，那麼 `animation-timing-function` 表述的就是車在運動中的加速和減速等過程。
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有一些預定義的關鍵字可用於常見的選項。 比如，默認值是 `ease`，動畫以低速開始，然後加快，在結束前變慢。 其它常用的值包括 `ease-out`：動畫以高速開始，以低速結束；`ease-in`，動畫以低速開始，以高速結束；`linear`：動畫從頭到尾的速度是相同的。
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# --instructions--
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給 id 爲 `ball1` 和 `ball2` 的元素添加 `animation-timing-function`，`ball1` 的屬性值爲 `linear`，`ball2` 的屬性值爲 `ease-out`。 它們的 `animation-duration` 都爲 2 秒，注意觀察它們在開始和結束時的不同。
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# --hints--
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id 爲 `ball1` 的元素的 `animation-timing-function` 屬性值應爲 `linear`。
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```js
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const ball1Animation = __helpers.removeWhiteSpace(
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$('#ball1').css('animation-timing-function')
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);
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assert(ball1Animation == 'linear' || ball1Animation == 'cubic-bezier(0,0,1,1)');
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```
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id 爲 `ball2` 的元素的 `animation-timing-function` 屬性值爲 `ease-out`。
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```js
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const ball2Animation = __helpers.removeWhiteSpace(
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$('#ball2').css('animation-timing-function')
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);
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assert(
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ball2Animation == 'ease-out' || ball2Animation == 'cubic-bezier(0,0,0.58,1)'
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);
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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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.balls {
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border-radius: 50%;
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background: linear-gradient(
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35deg,
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#ccffff,
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#ffcccc
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);
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position: fixed;
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width: 50px;
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height: 50px;
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margin-top: 50px;
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animation-name: bounce;
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animation-duration: 2s;
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animation-iteration-count: infinite;
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}
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#ball1 {
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left:27%;
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}
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#ball2 {
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left:56%;
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}
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@keyframes bounce {
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0% {
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top: 0px;
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}
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100% {
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top: 249px;
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}
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}
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</style>
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<div class="balls" id="ball1"></div>
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<div class="balls" id="ball2"></div>
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```
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# --solutions--
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```html
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<style>
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.balls {
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border-radius: 50%;
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background: linear-gradient(
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35deg,
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#ccffff,
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#ffcccc
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);
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position: fixed;
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width: 50px;
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height: 50px;
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margin-top: 50px;
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animation-name: bounce;
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animation-duration: 2s;
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animation-iteration-count: infinite;
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}
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#ball1 {
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left:27%;
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animation-timing-function: linear;
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}
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#ball2 {
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left:56%;
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animation-timing-function: ease-out;
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}
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@keyframes bounce {
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0% {
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top: 0px;
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}
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100% {
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top: 249px;
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}
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}
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</style>
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<div class="balls" id="ball1"></div>
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<div class="balls" id="ball2"></div>
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```
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