67 lines
1.7 KiB
JavaScript
67 lines
1.7 KiB
JavaScript
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let isEqual = require('lodash.isequal'),
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forEach = require('lodash.foreach'),
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isEmpty = require('lodash.isempty'),
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cloneObject = require('lodash.clone'),
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extendObject = require('lodash.assign'),
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debouncer = require("./Debouncer")
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function Scrllr(options) {
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options = extendObject(Scrllr.options, options)
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this.lastKnownScrollY = 0
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this.initialised = false
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this.onScrollCallback = options.onScrollCallback
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}
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Scrllr.prototype = {
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constructor : Scrllr,
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init : function() {
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this.debouncer = new debouncer(this.update.bind(this))
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// defer event registration to handle browser
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// potentially restoring previous scroll position
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setTimeout(this.attachEvent.bind(this), 100)
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return this
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},
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attachEvent : function() {
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if(!this.initialised) {
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this.lastKnownScrollY = this.getScrollY()
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this.initialised = true
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window.addEventListener('scroll', this.debouncer, false)
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this.debouncer.handleEvent()
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}
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},
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getScrollY : function() {
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return (window.pageYOffset !== undefined)
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? window.pageYOffset
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: (window.scrollTop !== undefined)
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? window.scrollTop
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: (document.documentElement || document.body.parentNode || document.body).scrollTop
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},
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update : function() {
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let currentScrollY = this.getScrollY(),
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scrollDirection = currentScrollY > this.lastKnownScrollY ? 'down' : 'up'
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this.onScrollCallback(currentScrollY)
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this.lastKnownScrollY = currentScrollY
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},
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destroy : function() {
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this.initialised = false
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window.removeEventListener('scroll', this.debouncer, false)
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}
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}
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Scrllr.options = {
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onScrollCallback: function(){}
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}
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module.exports = Scrllr
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