这是
实验性技术
检查
浏览器兼容性表格
要小心谨慎在生产中使用这之前。
Animation.startTime
特性为
动画
interface is a double-precision floating-point value which indicates the scheduled time when an animation's playback should begin.
An animation’s
start time
is the time value of its
DocumentTimeline
when its target
KeyframeEffect
is scheduled to begin playback. An animation’s
start time
is initially unresolved (meaning that it's
null
because it has no value).
var animationStartedWhen = Animation.startTime; Animation.startTime = newStartTime;
A floating-point number representing the current time in milliseconds, or
null
if no time is set. You can read this value to determine what the start time is currently set at, and you can change this value to make the animation start at a different time.
在
Running on Web Animations API example
, the we can sync all new animated cats by giving them all the same
startTime
as the original running cat:
var catRunning = document.getElementById ("withWAAPI").animate(keyframes, timing);
/* A function that makes new cats. */
function addCat(){
var newCat = document.createElement("div");
newCat.classList.add("cat");
return newCat;
}
/* This is the function that adds a cat to the WAAPI column */
function animateNewCatWithWAAPI() {
// make a new cat
var newCat = addCat();
// animate said cat with the WAAPI's "animate" function
var newAnimationPlayer = newCat.animate(keyframes, timing);
// set the animation's start time to be the same as the original .cat#withWAAPI
newAnimationPlayer.startTime = catRunning.startTime;
// Add the cat to the pile.
WAAPICats.appendChild(newCat);
}
To offer protection against timing attacks and fingerprinting, the precision of
animation.startTime
might get rounded depending on browser settings.
In Firefox, the
privacy.reduceTimerPrecision
preference is enabled by default and defaults to 20us in Firefox 59; in 60 it will be 2ms.
// reduced time precision (2ms) in Firefox 60 animation.startTime; // 23.404 // 24.192 // 25.514 // ... // reduced time precision with `privacy.resistFingerprinting` enabled animation.startTime; // 49.8 // 50.6 // 51.7 // ...
In Firefox, you can also enabled
privacy.resistFingerprinting
, the precision will be 100ms or the value of
privacy.resistFingerprinting.reduceTimerPrecision.microseconds
, whichever is larger.
| 规范 | 状态 | 注释 |
|---|---|---|
|
Web 动画
The definition of 'Animation.startTime' in that specification. |
工作草案 | 编者草案。 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
startTime
|
Chrome 39 | Edge ≤79 | Firefox 48 | IE 不支持 No | Opera 26 | Safari 不支持 No | WebView Android 39 | Chrome Android 39 | Firefox Android 48 | Opera Android 26 | Safari iOS 不支持 No | Samsung Internet Android 4.0 |
完整支持
不支持
实验。期望将来行为有所改变。
用户必须明确启用此特征。
动画
Animation.currentTime
for the current time of the animation.
动画