uni-Identify-quality/tm-vuetify/components/tm-flop/requestAnimationFrame.js

//此库移植自：https://github.com/sitonlotus/vue-digital-flop
let lastTime = 0
const prefixes = 'webkit moz ms o'.split(' ') // 各浏览器前缀

let requestAnimationFrame
let cancelAnimationFrame
let prefix
// #ifdef H5
requestAnimationFrame = window.requestAnimationFrame
cancelAnimationFrame = window.cancelAnimationFrame
// 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']
}
// #endif



// 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 = setTimeout(() => {
			callback(currTime + timeToCall)
		}, timeToCall)
		lastTime = currTime + timeToCall
		return id
	}

	cancelAnimationFrame = function(id) {
		clearTimeout(id)
	}
}

export {
	requestAnimationFrame,
	cancelAnimationFrame
}