Created
June 27, 2012 06:44
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setTimeout vs. nested-RAF
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| // 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 Möller | |
| // fixes from Paul Irish and Tino Zijdel | |
| (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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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <style> | |
| #foobar { position:absolute; left:0px; top:0px; width:200px; height:75px; background-color:#aaa; | |
| -moz-transition: -moz-transform 0.3s; -moz-transform: translate(200px, 5px) translateZ(0px) scale(1, 1); -moz-transform-origin: 0px 0px; | |
| -webkit-transition: -webkit-transform 0.3s; -webkit-transform: translate(200px, 5px) translateZ(0px) scale(1, 1); -webkit-transform-origin: 0px 0px; | |
| } | |
| #foobar.hidden { | |
| -moz-transition: -moz-transform 0.3s; -moz-transform: translate(200px, -100px) translateZ(0px) scale(1, 1); -moz-transform-origin: 0px 0px; | |
| -webkit-transition: -webkit-transform 0.3s; -webkit-transform: translate(200px, -100px) translateZ(0px) scale(1, 1); -webkit-transform-origin: 0px 0px; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="foobar"></div> | |
| </body> | |
| </html> |
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| function hide() { | |
| var foobar = document.getElementById("foobar"); | |
| foobar.className = "hidden"; | |
| foobar.addEventListener("transitionend",do_hide,true); | |
| foobar.addEventListener("webkitTransitionEnd",do_hide,true); | |
| } | |
| function do_hide() { | |
| var foobar = document.getElementById("foobar"); | |
| foobar.style.display = "none"; | |
| foobar.removeEventListener("transitionend",do_hide,true); | |
| foobar.removeEventListener("webkitTransitionEnd",do_hide,true); | |
| } | |
| // **************************************** | |
| // this is ugly! | |
| function show_1() { | |
| var foobar = document.getElementById("foobar"); | |
| foobar.style.display = "block"; | |
| setTimeout(function(){ | |
| foobar.className = ""; // remove 'hidden' class | |
| },50); | |
| } | |
| // BUT, is this actually better, or worse? | |
| function show_2() { | |
| var foobar = document.getElementById("foobar"); | |
| foobar.style.display = "block"; | |
| requestAnimationFrame(function(){ | |
| requestAnimationFrame(function(){ | |
| foobar.className = ""; // remove 'hidden' class | |
| }); | |
| }); | |
| } |
For future reference, if someone else comes here and is not sure why the nested rAF: it's because single rAF call would schedule the layout update for the current frame while the second rAF call inside the first one schedules the layout update for the next frame. The layout will be repainted between frames so in order to have the display = "block" happen before (on the previous frame) the className = "", nesting is needed. Otherwise both of the changes would happen on the same frame.
@piehei +1 yep! :)
@piehei +1! 🙏
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Hi,
this code works great, but I'm confused about the 'requestAnimationFrame'.
Could you explain why nesting a raf in another?
Thanks