182 lines
3.5 KiB
Markdown
182 lines
3.5 KiB
Markdown
---
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id: 587d78a8367417b2b2512ae4
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title: 使用无限的动画计数制作 CSS 心跳
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challengeType: 0
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videoUrl: 'https://scrimba.com/c/cDZpDUr'
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forumTopicId: 301062
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dashedName: make-a-css-heartbeat-using-an-infinite-animation-count
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---
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# --description--
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这也是一个用 `animation-iteration-count` 属性创造持续动画的例子，它基于我们在前面挑战中创建的心形。
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心跳动画的每一秒包含两个部分。`heart` 元素（包括 `:before` 和 `:after`）使用 `transform` 属性改变其大小，背景 `div` 使用 `background` 属性改变其颜色。
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# --instructions--
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请将 class 为 `back` 和 `heart` 的元素的 `animation-iteration-count` 属性值设置为 infinite，使心形可以持续跳动。`heart:before` 和 `heart:after` 所选择的元素则不需要添加动画属性。
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# --hints--
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class 为 `heart` 的元素的 `animation-iteration-count` 属性值应为 infinite。
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```js
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assert($('.heart').css('animation-iteration-count') == 'infinite');
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```
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class 为 `back` 的元素的 `animation-iteration-count` 属性值应为 infinite。
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```js
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assert($('.back').css('animation-iteration-count') == 'infinite');
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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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.back {
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position: fixed;
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padding: 0;
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margin: 0;
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top: 0;
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left: 0;
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width: 100%;
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height: 100%;
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background: white;
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animation-name: backdiv;
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animation-duration: 1s;
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}
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.heart {
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position: absolute;
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margin: auto;
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top: 0;
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right: 0;
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bottom: 0;
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left: 0;
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background-color: pink;
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height: 50px;
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width: 50px;
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transform: rotate(-45deg);
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animation-name: beat;
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animation-duration: 1s;
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}
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.heart:after {
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background-color: pink;
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content: "";
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border-radius: 50%;
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position: absolute;
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width: 50px;
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height: 50px;
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top: 0px;
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left: 25px;
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}
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.heart:before {
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background-color: pink;
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content: "";
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border-radius: 50%;
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position: absolute;
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width: 50px;
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height: 50px;
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top: -25px;
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left: 0px;
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}
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@keyframes backdiv {
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50% {
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background: #ffe6f2;
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}
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}
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@keyframes beat {
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0% {
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transform: scale(1) rotate(-45deg);
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}
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50% {
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transform: scale(0.6) rotate(-45deg);
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}
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}
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</style>
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<div class="back"></div>
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<div class="heart"></div>
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```
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# --solutions--
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```html
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<style>
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.back {
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position: fixed;
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padding: 0;
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margin: 0;
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top: 0;
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left: 0;
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width: 100%;
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height: 100%;
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background: white;
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animation-name: backdiv;
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animation-duration: 1s;
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animation-iteration-count: infinite;
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}
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.heart {
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position: absolute;
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margin: auto;
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top: 0;
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right: 0;
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bottom: 0;
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left: 0;
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background-color: pink;
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height: 50px;
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width: 50px;
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transform: rotate(-45deg);
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animation-name: beat;
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animation-duration: 1s;
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animation-iteration-count: infinite;
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}
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.heart:after {
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background-color: pink;
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content: "";
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border-radius: 50%;
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position: absolute;
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width: 50px;
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height: 50px;
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top: 0px;
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left: 25px;
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}
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.heart:before {
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background-color: pink;
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content: "";
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border-radius: 50%;
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position: absolute;
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width: 50px;
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height: 50px;
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top: -25px;
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left: 0px;
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}
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@keyframes backdiv {
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50% {
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background: #ffe6f2;
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}
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}
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@keyframes beat {
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0% {
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transform: scale(1) rotate(-45deg);
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}
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50% {
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transform: scale(0.6) rotate(-45deg);
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}
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}
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</style>
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<div class="back"></div>
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<div class="heart"></div>
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```
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