discourse/vendor/assets/javascripts/lock-on.js

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JavaScript
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(function (exports) {
var scrollEvents = "scroll.lock-on touchmove.lock-on mousedown.lock-on wheel.lock-on DOMMouseScroll.lock-on mousewheel.lock-on keyup.lock-on";
var LockOn = function(selector, options) {
this.selector = selector;
this.options = options || {};
};
LockOn.prototype.elementTop = function() {
var offsetCalculator = this.options.offsetCalculator,
selected = $(this.selector);
if (selected && selected.offset && selected.offset()) {
return selected.offset().top - (offsetCalculator ? offsetCalculator() : 0);
}
};
LockOn.prototype.lock = function() {
var self = this,
previousTop = this.elementTop(),
startedAt = new Date().getTime()
i = 0;
$(window).scrollTop(previousTop);
var interval = setInterval(function() {
i = i + 1;
var top = self.elementTop(),
scrollTop = $(window).scrollTop();
if (typeof(top) === "undefined") {
$('body,html').off(scrollEvents)
clearInterval(interval);
return;
}
if ((top !== previousTop) || (scrollTop !== top)) {
$(window).scrollTop(top);
previousTop = top;
}
// We commit suicide after 1s just to clean up
var nowTime = new Date().getTime();
if (nowTime - startedAt > 1000) {
$('body,html').off(scrollEvents)
clearInterval(interval);
}
}, 50);
$('body,html').off(scrollEvents).on(scrollEvents, function(e){
if ( e.which > 0 || e.type === "mousedown" || e.type === "mousewheel" || e.type === "touchmove") {
$('body,html').off(scrollEvents);
clearInterval(interval);
}
})
};
exports.LockOn = LockOn;
})(window);