JS使用window.requestAnimationFrame()實(shí)現(xiàn)逐幀動(dòng)畫
window.requestAnimationFrame() 方法告訴瀏覽器您希望執(zhí)行動(dòng)畫,并請求瀏覽器調(diào)用指定的函數(shù)在下一次重繪之前更新動(dòng)畫。該方法使用一個(gè)回調(diào)函數(shù)作為參數(shù),這個(gè)回調(diào)函數(shù)會(huì)在瀏覽器重繪之前調(diào)用。
如果你想做逐幀動(dòng)畫的時(shí)候,你應(yīng)該用這個(gè)方法。這就要求你的動(dòng)畫函數(shù)執(zhí)行會(huì)先于瀏覽器重繪動(dòng)作。通常來說,被調(diào)用的頻率是每秒60次,但是一般會(huì)遵循W3C標(biāo)準(zhǔn)規(guī)定的頻率。如果是后臺(tái)標(biāo)簽頁面,重繪頻率則會(huì)大大降低。
基本語法:
requestID = window.requestAnimationFrame(callback); // Firefox 23 / IE10 / Chrome / Safari 7 (incl. iOS) requestID = window.mozRequestAnimationFrame(callback); // Firefox < 23 requestID = window.webkitRequestAnimationFrame(callback); // Older versions Chrome/Webkit
瀏覽器支持情況:
下面通過兩個(gè)簡單的Demo介紹下window.requestAnimationFrame() 方法的使用
返回頂部
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>返回頂部</title> <style> .box { margin: 0 auto; width: 100%; height: 5000px; } .box1 { background: #b94a48; } .box2 { background: #fb8c00; } .box3 { background: #669900; } .box4 { background: #c0a16b; } .top { position: fixed; right: 20px; bottom: 20px; width: 40px; height: 40px; background: #8dc7ff; border-radius: 50%; cursor: pointer; } </style> <script> window.requestAnimationFrame = (function () { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function (callback) { window.setTimeout(callback, 6000 / 60) } })() window.cancelAnimFrame = (function () { return window.cancelAnimationFrame || window.webkitCancelAnimationFrame || window.mozCancelAnimationFrame || window.oCancelAnimationFrame || window.msCancelAnimationFrame || function (callback) { window.clearTimeout(callback) } })() function scrollToTop() { let top = window.pageYOffset const duration = 320 const step = top / (duration / (1000 / 60)) >> 0 const fn = () => { if (top >= 0) { top -= step window.scrollTo(0, top) fn.rafTimer = window.requestAnimationFrame(fn) } else { window.scrollTo(0, 0) window.cancelAnimationFrame(fn.rafTimer) } } fn.rafTimer = window.requestAnimationFrame(fn) } </script> </head> <body> <div class="box box1"></div> <div class="box box2"></div> <div class="box box3"></div> <div class="box box4"></div> <div class="top" onclick="scrollToTop()"></div> </body> </html>
錨點(diǎn)定位
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>錨點(diǎn)定位</title> <style> .top { margin: 100px auto; cursor: pointer; } .top1 { color: #b94a48; } .top2 { color: #fb8c00; } .top3 { color: #669900; } .top4 { color: #c0a16b; } .box { margin: 0 auto; width: 100%; height: 5000px; } .box1 { background: #b94a48; } .box2 { background: #fb8c00; } .box3 { background: #669900; } .box4 { background: #c0a16b; } </style> <script> window.requestAnimationFrame = (function () { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function (callback) { window.setTimeout(callback, 6000 / 60) } })() window.cancelAnimFrame = (function () { return window.cancelAnimationFrame || window.webkitCancelAnimationFrame || window.mozCancelAnimationFrame || window.oCancelAnimationFrame || window.msCancelAnimationFrame || function (callback) { window.clearTimeout(callback) } })() function goPosition(index) { let top = 0 let distance = document.getElementById(index).offsetTop const duration = 320 const step = distance / (duration / (1000 / 60)) >> 0 const fn = () => { if (distance >= top) { top += step window.scrollTo(0, top) fn.rafTimer = window.requestAnimationFrame(fn) } else { window.cancelAnimationFrame(fn.rafTimer) } } fn.rafTimer = window.requestAnimationFrame(fn) } </script> </head> <body> <div class="top top1" onclick="goPosition('box1')">跳到第一個(gè)</div> <div class="top top2" onclick="goPosition('box2')">跳到第二個(gè)</div> <div class="top top3" onclick="goPosition('box3')">跳到第三個(gè)</div> <div class="top top4" onclick="goPosition('box4')">跳到第四個(gè)</div> <div id="box1" class="box box1"></div> <div id="box2" class="box box2"></div> <div id="box3" class="box box3"></div> <div id="box4" class="box box4"></div> </body> </html>
網(wǎng)上技術(shù)大牛針對瀏覽器兼容封裝源碼:
// http://paulirish.com/2011/requestanimationframe-for-smart-animating/ // http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating // requestAnimationFrame polyfill by Erik M?ller. fixes from Paul Irish and Tino Zijdel // MIT license (function() { var lastTime = 0; var vendors = ['ms', 'moz', 'webkit', 'o']; for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) { window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame']; window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame']; } if (!window.requestAnimationFrame) window.requestAnimationFrame = function(callback, element) { var currTime = new Date().getTime(); var timeToCall = Math.max(0, 16 - (currTime - lastTime)); var id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall); lastTime = currTime + timeToCall; return id; }; if (!window.cancelAnimationFrame) window.cancelAnimationFrame = function(id) { clearTimeout(id); }; }());
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