元素:animationstart 事件

CSS 动画 开始时,将触发 animationstart 事件。如果存在 animation-delay,则此事件将在延迟期满后触发。负延迟将导致事件触发,其 elapsedTime 等于延迟的绝对值(相应地,动画将从该时间索引开始播放到序列中)。

语法

在诸如 addEventListener() 之类的方法中使用事件名称,或设置事件处理程序属性。

js
addEventListener("animationstart", (event) => {});

onanimationstart = (event) => {};

事件类型

事件属性

还继承了其父级 Event 的属性.

AnimationEvent.animationName 只读

一个字符串,包含生成动画的 animation-name 的值。

AnimationEvent.elapsedTime 只读

一个 float,表示触发此事件时动画已运行的时间量(以秒为单位),不包括动画暂停的任何时间。对于 animationstart 事件,elapsedTime0.0,除非 animation-delay 的值为负数,在这种情况下,事件将以 elapsedTime 包含 (-1 * delay) 的方式触发。

AnimationEvent.pseudoElement 只读

一个以'::'开头的字符串,包含动画运行的伪元素的名称。如果动画不是在伪元素上运行,而是在元素上运行,则为空字符串:''

示例

这段代码监听animationstart事件,并在事件触发时记录一条消息。

js
const animated = document.querySelector(".animated");

animated.addEventListener("animationstart", () => {
  console.log("Animation started");
});

与上例相同,但使用onanimationstart

js
const animated = document.querySelector(".animated");

animated.onanimationstart = () => {
  console.log("Animation started");
};

在线示例

HTML

html
<div class="animation-example">
  <div class="container">
    <p class="animation">You chose a cold night to visit our planet.</p>
  </div>
  <button class="activate" type="button">Activate animation</button>
  <div class="event-log"></div>
</div>

CSS

css
.container {
  height: 3rem;
}

.event-log {
  width: 25rem;
  height: 2rem;
  border: 1px solid black;
  margin: 0.2rem;
  padding: 0.2rem;
}

.animation.active {
  animation-duration: 2s;
  animation-name: slidein;
  animation-iteration-count: 2;
}

@keyframes slidein {
  from {
    transform: translateX(100%) scaleX(3);
  }
  to {
    transform: translateX(0) scaleX(1);
  }
}

JavaScript

js
const animation = document.querySelector("p.animation");
const animationEventLog = document.querySelector(
  ".animation-example>.event-log",
);
const applyAnimation = document.querySelector(
  ".animation-example>button.activate",
);
let iterationCount = 0;

animation.addEventListener("animationstart", () => {
  animationEventLog.textContent = `${animationEventLog.textContent}'animation started' `;
});

animation.addEventListener("animationiteration", () => {
  iterationCount++;
  animationEventLog.textContent = `${animationEventLog.textContent}'animation iterations: ${iterationCount}' `;
});

animation.addEventListener("animationend", () => {
  animationEventLog.textContent = `${animationEventLog.textContent}'animation ended'`;
  animation.classList.remove("active");
  applyAnimation.textContent = "Activate animation";
});

animation.addEventListener("animationcancel", () => {
  animationEventLog.textContent = `${animationEventLog.textContent}'animation canceled'`;
});

applyAnimation.addEventListener("click", () => {
  animation.classList.toggle("active");
  animationEventLog.textContent = "";
  iterationCount = 0;
  const active = animation.classList.contains("active");
  applyAnimation.textContent = active
    ? "Cancel animation"
    : "Activate animation";
});

结果

规范

规范
CSS 动画级别 1
# eventdef-globaleventhandlers-animationstart

浏览器兼容性

BCD 表格仅在浏览器中加载

另请参阅