-import { Directive, EventEmitter, Input, OnInit, Output } from '@angular/core'
-import 'rxjs/add/operator/distinct'
-import 'rxjs/add/operator/startWith'
-import { fromEvent } from 'rxjs/observable/fromEvent'
+import { distinct, distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators'
+import { Directive, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core'
+import { fromEvent, Subscription } from 'rxjs'
@Directive({
selector: '[myInfiniteScroller]'
})
-export class InfiniteScrollerDirective implements OnInit {
- private static PAGE_VIEW_TOP_MARGIN = 500
-
+export class InfiniteScrollerDirective implements OnInit, OnDestroy {
@Input() containerHeight: number
@Input() pageHeight: number
+ @Input() firstLoadedPage = 1
@Input() percentLimit = 70
- @Input() autoLoading = false
+ @Input() autoInit = false
@Output() nearOfBottom = new EventEmitter<void>()
@Output() nearOfTop = new EventEmitter<void>()
private decimalLimit = 0
private lastCurrentBottom = -1
private lastCurrentTop = 0
+ private scrollDownSub: Subscription
+ private scrollUpSub: Subscription
+ private pageChangeSub: Subscription
+ private middleScreen: number
constructor () {
this.decimalLimit = this.percentLimit / 100
}
ngOnInit () {
- if (this.autoLoading === true) return this.initialize()
+ if (this.autoInit === true) return this.initialize()
+ }
+
+ ngOnDestroy () {
+ if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
+ if (this.scrollUpSub) this.scrollUpSub.unsubscribe()
+ if (this.pageChangeSub) this.pageChangeSub.unsubscribe()
}
initialize () {
+ this.middleScreen = window.innerHeight / 2
+
+ // Emit the last value
+ const throttleOptions = { leading: true, trailing: true }
+
const scrollObservable = fromEvent(window, 'scroll')
- .startWith(true)
- .map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight }))
+ .pipe(
+ startWith(null),
+ throttleTime(200, undefined, throttleOptions),
+ map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight })),
+ distinctUntilChanged((o1, o2) => o1.current === o2.current),
+ share()
+ )
// Scroll Down
- scrollObservable
- // Check we scroll down
- .filter(({ current }) => {
- const res = this.lastCurrentBottom < current
-
- this.lastCurrentBottom = current
- return res
- })
- .filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit)
- .debounceTime(200)
- .distinct()
+ this.scrollDownSub = scrollObservable
+ .pipe(
+ // Check we scroll down
+ filter(({ current }) => {
+ const res = this.lastCurrentBottom < current
+
+ this.lastCurrentBottom = current
+ return res
+ }),
+ filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit)
+ )
.subscribe(() => this.nearOfBottom.emit())
// Scroll up
- scrollObservable
- // Check we scroll up
- .filter(({ current }) => {
- const res = this.lastCurrentTop > current
-
- this.lastCurrentTop = current
- return res
- })
- .filter(({ current, maximumScroll }) => {
- return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit
- })
- .debounceTime(200)
- .distinct()
+ this.scrollUpSub = scrollObservable
+ .pipe(
+ // Check we scroll up
+ filter(({ current }) => {
+ const res = this.lastCurrentTop > current
+
+ this.lastCurrentTop = current
+ return res
+ }),
+ filter(({ current, maximumScroll }) => {
+ return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit
+ })
+ )
.subscribe(() => this.nearOfTop.emit())
// Page change
- scrollObservable
- .debounceTime(500)
- .distinct()
- .map(({ current }) => Math.max(1, Math.round((current + InfiniteScrollerDirective.PAGE_VIEW_TOP_MARGIN) / this.pageHeight)))
- .distinctUntilChanged()
+ this.pageChangeSub = scrollObservable
+ .pipe(
+ distinct(),
+ map(({ current }) => this.calculateCurrentPage(current)),
+ distinctUntilChanged()
+ )
.subscribe(res => this.pageChanged.emit(res))
}
+ private calculateCurrentPage (current: number) {
+ const scrollY = current + this.middleScreen
+
+ const page = Math.max(1, Math.ceil(scrollY / this.pageHeight))
+
+ // Offset page
+ return page + (this.firstLoadedPage - 1)
+ }
}