I'm using Skrollr-menu to animate down a page on a button press using the following
HTML
<a href="#End"><div class="trigger-scroll left">></div></a>
... the page i want to reveal, using scrolling ...
<section id="End" class="scroll-here">
<div class="hsContainer bottom"></div>
</section>
JavaScript
var s = skrollr.init();
skrollr.menu.init(s, {
animate: true,
//How long the animation should take in ms.
duration: function(currentTop, targetTop) {
//By default, the duration is hardcoded at 500ms.
return 18000;
//But you could calculate a value based on the current scroll position (`currentTop`) and the target scroll position (`targetTop`).
//return Math.abs(currentTop - targetTop) * 10;
},
//This event is triggered right before we jump/animate to a new hash.
change: function(newHash, newTopPosition) {
//Do stuff
},
//Add hash link (e.g. `#foo`) to URL or not.
updateUrl: false //defaults to `true`.
});
What happens when I click the button is that it works, that is not the problem.
The problem is that it seems to change speed as skrollr-menu animates the page. It starts off quite quickly, which means that the first few elements on the page (about the first 2000px) flash past without being readable. Then the speed evens out and is fine right until the last 3000px (approximately) where skrollr-menu is very slow. What I want is for the click of the button to resemble holding the down arrow on the keyboard or the scroll sidebar, which by default it seems skrollr-menu does not do.
I've tried using math equations to change the speed but the issue persists no matter what i try, and there doesn't seem to be any "simple" way to change the acceleration speed, and I suspect the problem is somewhere within the Skrollr.menu.js file, but I can't see where.
Is there any way which I can make the scrolling an even speed, rather than fast at the start and slow at the end?
Note: I'm not very experienced in JavaScript or jQuery, so it's probably something simple I've overlooked.
skrollr menu on github https://github.com/Prinzhorn/skrollr-menu
Skrollr.menu.js
/*!
* Plugin for skrollr.
* This plugin makes hashlinks scroll nicely to their target position.
*
* Alexander Prinzhorn - https://github.com/Prinzhorn/skrollr
*
* Free to use under terms of MIT license
*/
(function(document, window) {
'use strict';
var DEFAULT_DURATION = 500;
var DEFAULT_EASING = 'sqrt';
var DEFAULT_SCALE = 1;
var MENU_TOP_ATTR = 'data-menu-top';
var MENU_OFFSET_ATTR = 'data-menu-offset';
var MENU_DURATION_ATTR = 'data-menu-duration';
var MENU_IGNORE_ATTR = 'data-menu-ignore';
var skrollr = window.skrollr;
var history = window.history;
var supportsHistory = !!history.pushState;
/*
Since we are using event bubbling, the element that has been clicked
might not acutally be the link but a child.
*/
var findParentLink = function(element) {
//We reached the top, no link found.
if(element === document) {
return false;
}
//Yay, it's a link!
if(element.tagName.toUpperCase() === 'A') {
return element;
}
//Maybe the parent is a link.
return findParentLink(element.parentNode);
};
/*
Handle the click event on the document.
*/
var handleClick = function(e) {
//Only handle left click.
if(e.which !== 1 && e.button !== 0) {
return;
}
var link = findParentLink(e.target);
//The click did not happen inside a link.
if(!link) {
return;
}
if(handleLink(link)) {
e.preventDefault();
}
};
/*
Handles the click on a link. May be called without an actual click event.
When the fake flag is set, the link won't change the url and the position won't be animated.
*/
var handleLink = function(link, fake) {
var hash;
//When complexLinks is enabled, we also accept links which do not just contain a simple hash.
if(_complexLinks) {
//The link points to something completely different.
if(link.hostname !== window.location.hostname) {
return false;
}
//The link does not link to the same page/path.
if(link.pathname !== document.location.pathname) {
return false;
}
hash = link.hash;
} else {
//Don't use the href property (link.href) because it contains the absolute url.
hash = link.getAttribute('href');
}
//Not a hash link.
if(!/^#/.test(hash)) {
return false;
}
//The link has the ignore attribute.
if(!fake && link.getAttribute(MENU_IGNORE_ATTR) !== null) {
return false;
}
//Now get the targetTop to scroll to.
var targetTop;
var menuTop;
//If there's a handleLink function, it overrides the actual anchor offset.
if(_handleLink) {
menuTop = _handleLink(link);
}
//If there's a data-menu-top attribute and no handleLink function, it overrides the actual anchor offset.
else {
menuTop = link.getAttribute(MENU_TOP_ATTR);
}
if(menuTop !== null) {
//Is it a percentage offset?
if(/p$/.test(menuTop)) {
targetTop = (menuTop.slice(0, -1) / 100) * document.documentElement.clientHeight;
} else {
targetTop = +menuTop * _scale;
}
} else {
var scrollTarget = document.getElementById(hash.substr(1));
//Ignore the click if no target is found.
if(!scrollTarget) {
return false;
}
targetTop = _skrollrInstance.relativeToAbsolute(scrollTarget, 'top', 'top');
var menuOffset = scrollTarget.getAttribute(MENU_OFFSET_ATTR);
if(menuOffset !== null) {
targetTop += +menuOffset;
}
}
if(supportsHistory && _updateUrl && !fake) {
history.pushState({top: targetTop}, '', hash);
}
var menuDuration = parseInt(link.getAttribute(MENU_DURATION_ATTR), 10);
var animationDuration = _duration(_skrollrInstance.getScrollTop(), targetTop);
if(!isNaN(menuDuration)) {
animationDuration = menuDuration;
}
//Trigger the change if event if there's a listener.
if(_change) {
_change(hash, targetTop);
}
//Now finally scroll there.
if(_animate && !fake) {
_skrollrInstance.animateTo(targetTop, {
duration: animationDuration,
easing: _easing
});
} else {
defer(function() {
_skrollrInstance.setScrollTop(targetTop);
});
}
return true;
};
var jumpStraightToHash = function() {
if(window.location.hash && document.querySelector) {
var link = document.querySelector('a[href="' + window.location.hash + '"]');
if(!link) {
// No link found on page, so we create one and then activate it
link = document.createElement('a');
link.href = window.location.hash;
}
handleLink(link, true);
}
};
var defer = function(fn) {
window.setTimeout(fn, 1);
};
/*
Global menu function accessible through window.skrollr.menu.init.
*/
skrollr.menu = {};
skrollr.menu.init = function(skrollrInstance, options) {
_skrollrInstance = skrollrInstance;
options = options || {};
_easing = options.easing || DEFAULT_EASING;
_animate = options.animate !== false;
_duration = options.duration || DEFAULT_DURATION;
_handleLink = options.handleLink;
_scale = options.scale || DEFAULT_SCALE;
_complexLinks = options.complexLinks === true;
_change = options.change;
_updateUrl = options.updateUrl !== false;
if(typeof _duration === 'number') {
_duration = (function(duration) {
return function() {
return duration;
};
}(_duration));
}
//Use event bubbling and attach a single listener to the document.
skrollr.addEvent(document, 'click', handleClick);
if(supportsHistory) {
skrollr.addEvent(window, 'popstate', function(e) {
var state = e.state || {};
var top = state.top || 0;
defer(function() {
_skrollrInstance.setScrollTop(top);
});
}, false);
}
jumpStraightToHash();
};
//Expose the handleLink function to be able to programmatically trigger clicks.
skrollr.menu.click = function(link) {
//We're not assigning it directly to `click` because of the second ("private") parameter.
handleLink(link);
};
//Private reference to the initialized skrollr.
var _skrollrInstance;
var _easing;
var _duration;
var _animate;
var _handleLink;
var _scale;
var _complexLinks;
var _change;
var _updateUrl;
//In case the page was opened with a hash, prevent jumping to it.
//http://stackoverflow.com/questions/3659072/jquery-disable-anchor-jump-when-loading-a-page
defer(function() {
if(window.location.hash) {
window.scrollTo(0, 0);
}
});
}(document, window));
