requestAnimationFrame.js
1.6 KB
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let lastTime = 0
const prefixes = 'webkit moz ms o'.split(' ') // 各浏览器前缀
let requestAnimationFrame
let cancelAnimationFrame
const isServer = typeof window === 'undefined'
if (isServer) {
requestAnimationFrame = function() {
return
}
cancelAnimationFrame = function() {
return
}
} else {
requestAnimationFrame = window.requestAnimationFrame
cancelAnimationFrame = window.cancelAnimationFrame
let prefix
// 通过遍历各浏览器前缀，来得到requestAnimationFrame和cancelAnimationFrame在当前浏览器的实现形式
for (let i = 0; i < prefixes.length; i++) {
if (requestAnimationFrame && cancelAnimationFrame) { break }
prefix = prefixes[i]
requestAnimationFrame = requestAnimationFrame || window[prefix + 'RequestAnimationFrame']
cancelAnimationFrame = cancelAnimationFrame || window[prefix + 'CancelAnimationFrame'] || window[prefix + 'CancelRequestAnimationFrame']
}
// 如果当前浏览器不支持requestAnimationFrame和cancelAnimationFrame，则会退到setTimeout
if (!requestAnimationFrame || !cancelAnimationFrame) {
requestAnimationFrame = function(callback) {
const currTime = new Date().getTime()
// 为了使setTimteout的尽可能的接近每秒60帧的效果
const timeToCall = Math.max(0, 16 - (currTime - lastTime))
const id = window.setTimeout(() => {
callback(currTime + timeToCall)
}, timeToCall)
lastTime = currTime + timeToCall
return id
}
cancelAnimationFrame = function(id) {
window.clearTimeout(id)
}
}
}
export { requestAnimationFrame, cancelAnimationFrame }