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mhils/animatedScrollTo.js

Last active April 10, 2017 18:03
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animatedScrollTo.js
(function (window) {
var requestAnimFrame = (function(){return window.requestAnimationFrame||window.webkitRequestAnimationFrame||window.mozRequestAnimationFrame||function(callback){window.setTimeout(callback,1000/60);};})();
var easeInOutQuad = function (t, b, c, d) {
t /= d/2;
if (t < 1) return c/2*t*t + b;
t--;
return -c/2 * (t*(t-2) - 1) + b;
};
var animatedScrollTo = function (element, to, duration, callback) {
var start = element.scrollTop,
change = to - start,
animationStart = +new Date();
var animating = true;
var animateScroll = function() {
if (!animating) {
return;
}
requestAnimFrame(animateScroll);
var now = +new Date();
var val = Math.floor(easeInOutQuad(now - animationStart, start, change, duration));
element.scrollTop = val;
if (now > animationStart + duration) {
element.scrollTop = to;
animating = false;
if (callback) { callback(); }
}
};
requestAnimFrame(animateScroll);
};
if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
module.exports = animatedScrollTo;
} else {
window.animatedScrollTo = animatedScrollTo;
}
})(window);
Raw
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Presentation</title>
<style type="text/css">
html, body, #container {
margin: 0;
height: 100%;
width: 100%;
}
#container {
overflow: auto;
}
.pad {
flex-direction: column;
justify-content: center;
height: 100%;
display: flex;
text-align: center;
font-size: 80px;
color: gray;
}
img {
max-width: 100%;
}
::-webkit-scrollbar {
display: none;
}
</style>
<script type="text/javascript" src="./animatedScrollTo.js"></script>
<script type="text/javascript">
/* ------------- */
/* CONFIGURATION */
var stops = [0, 0.1, 0.5, 0.9, 1];
var scrollSpeed = 500;
/* ------------- */
/* ------------- */
var NEXT_KEYS = [32 /*SPACE*/, 34 /*PAGE DOWN*/ , 39 /*RIGHT*/, 40 /*DOWN*/],
PREV_KEYS = [8 /*BACKSPACE*/, 33 /* PAGE UP*/, 37 /*LEFT*/, 38 /*UP*/];
document.addEventListener("DOMContentLoaded", function(event) {
var image = document.getElementById("presentation");
var container = document.getElementById("container");
scrollTo(container, 0);
document.addEventListener("keydown", function(event) {
var isNext = NEXT_KEYS.indexOf(event.keyCode) > -1,
isPrev = PREV_KEYS.indexOf(event.keyCode) > -1;
if(isNext || isPrev) {
var docPos = container.scrollTop,
docHeight = container.offsetHeight,
docBottom = docPos + docHeight,
imgStart = image.offsetTop,
imgHeight = image.height,
done = (docBottom - imgStart) / imgHeight,
prev;
if(isPrev) {
done -= 1 / imgHeight;
prev = 1;
} else {
done += 1 / imgHeight;
prev = 0;
}
console.log("current state is", done, "at", docPos);
function scroll(percentage) {
var y = (percentage * imgHeight) + imgStart - docHeight;
console.log("scrolling to", percentage, "at", y);
animatedScrollTo(container, y, scrollSpeed);
}
for(var i=0; i < stops.length; i++) {
if(stops[i] > done){
scroll(stops[i - prev]);
break;
}
}
event.preventDefault();
} else {
console.log(event);
}
});
});
</script>
</head>
<body>
<div id="container">
<div class="pad">&darr;</div>
<img id="presentation" src="presentation.jpg">
</div>
</body>
</html>
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