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Rebase scroll.js

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Chuck Dries 2017-02-16 19:29:19 -07:00
parent 26cf76f9f2
commit 7f19287781
1 changed files with 30 additions and 33 deletions
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17
scroll.js
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@ -4,30 +4,27 @@ var speed = .0005; //speed multiplier
//setup necissary stuff //setup necissary stuff
var target = null; var target = null;
var targetHeight = null; var targetHeight = null;
var prevHeight = null;
var currentHeight = null; var currentHeight = null;
var startTime = null; var startTime = null;
/* does some basic checking then calls animate() to do the heavy lifting */ /* does some basic checking then calls animate() to do the heavy lifting */
function smoothScroll(targetId) { function smoothScroll(targetId){
target = document.getElementById(targetId);//grab the element target = document.getElementById(targetId);//grab the element
targetHeight = target.offsetTop; //get its height targetHeight = target.offsetTop; //get its height
currentHeight = getScrollY(); //grab the current scroll position currentHeight = window.scrollY; //grab the current scroll position
prevHeight = null;
startTime = null; //we have to reset the start time every time the animation runs startTime = null; //we have to reset the start time every time the animation runs
if (currentHeight != targetHeight) { if(currentHeight != targetHeight){
window.requestAnimationFrame(animateScroll);//schedule the animation window.requestAnimationFrame(animateScroll);//schedule the animation
} }
} }
function animateScroll(timeStamp) { function animateScroll(timeStamp){
if (startTime == null) startTime = timeStamp; //record the time the animation started if we're just starting if (startTime == null) startTime = timeStamp; //record the time the animation started if we're just starting
var deltaStep = (timeStamp - startTime) * speed; //timeStamp - startTime gives us miliseconds since the animation started, we scale this down because its usually in the hundreds. var deltaStep = (timeStamp - startTime) * speed; //timeStamp - startTime gives us miliseconds since the animation started, we scale this down because its usually in the hundreds.
currentHeight = getScrollY(); //record the current scroll position of the window currentHeight = window.scrollY; //record the current scroll position of the window
prevHeight = currentHeight;//store height before scroll action so we can compare it to the height after we try to scroll
var offsetScroll = targetHeight - currentHeight; //calculate how far we still need to go var offsetScroll = targetHeight - currentHeight; //calculate how far we still need to go
var deltaScroll = deltaStep * offsetScroll; //decide how far to scroll this tick var deltaScroll = deltaStep * offsetScroll; //decide how far to scroll this tick
window.scroll(0, currentHeight + deltaScroll); //scroll! window.scroll(0, currentHeight + deltaScroll); //scroll!
currentHeight = getScrollY();//re-record the current height after scrolling for comparison currentHeight = window.scrollY;//re-record the current height after scrolling for comparison
if ((currentHeight != targetHeight) && ((currentHeight != prevHeight) || (deltaStep == 0))) { //schedule another tick until we get where we're going or we get as far as we can. deltastep will always be 0 on the first frame. if(Math.floor(currentHeight) != Math.floor(targetHeight)){ //schedule another tick if we need to
window.requestAnimationFrame(animateScroll); window.requestAnimationFrame(animateScroll);
} }