Created
March 19, 2013 22:21
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scrollToPos ( yPos, opts, after );
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| /* | |
| Props to emilejs for nice handling of easing and callbacks. | |
| TODO: | |
| opts.el - calculate positions | |
| (in our case, we do that outside of this function already) | |
| IE8+ ... el = (typeof el === 'string') ? document.querySelector(el) : el | |
| use window.requestAnimationFrame instead of setInterval | |
| - with polyfill of course | |
| */ | |
| function scrollToPos(yPos, opts, after){ | |
| var opts = opts || {}, | |
| duration = opts.duration || 600, | |
| threshold = opts.threshold || 100, | |
| easing = opts.easing || function(pos){return(-Math.cos(pos*Math.PI)/2)+0.5;}, | |
| startTime = +new Date, | |
| finish = startTime + duration, | |
| startY = isNaN(window.pageYOffset) ? document.documentElement.scrollTop : window.pageYOffset, | |
| distance = yPos - startY; | |
| if (Math.abs(distance) < threshold) { | |
| window.scrollTo(0, yPos); | |
| return; | |
| } | |
| var interval = setInterval(function(){ | |
| var time = +new Date, | |
| pos = time > finish ? 1 : (time-startTime) / duration; | |
| window.scrollTo(0, startY + distance * easing(pos)); | |
| if(time > finish) { | |
| clearInterval(interval); | |
| opts.after && opts.after(); | |
| after && setTimeout(after,1); | |
| } | |
| }, 15); | |
| }; |
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