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1 | import { distinct, distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators' | |
2 | import { Directive, ElementRef, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core' | |
3 | import { fromEvent, Subscription } from 'rxjs' | |
4 | ||
5 | @Directive({ | |
6 | selector: '[myInfiniteScroller]' | |
7 | }) | |
8 | export class InfiniteScrollerDirective implements OnInit, OnDestroy { | |
9 | @Input() percentLimit = 70 | |
10 | @Input() autoInit = false | |
11 | @Input() onItself = false | |
12 | ||
13 | @Output() nearOfBottom = new EventEmitter<void>() | |
14 | ||
15 | private decimalLimit = 0 | |
16 | private lastCurrentBottom = -1 | |
17 | private scrollDownSub: Subscription | |
18 | private container: HTMLElement | |
19 | ||
20 | constructor (private el: ElementRef) { | |
21 | this.decimalLimit = this.percentLimit / 100 | |
22 | } | |
23 | ||
24 | ngOnInit () { | |
25 | if (this.autoInit === true) return this.initialize() | |
26 | } | |
27 | ||
28 | ngOnDestroy () { | |
29 | if (this.scrollDownSub) this.scrollDownSub.unsubscribe() | |
30 | } | |
31 | ||
32 | initialize () { | |
33 | if (this.onItself) { | |
34 | this.container = this.el.nativeElement | |
35 | } | |
36 | ||
37 | // Emit the last value | |
38 | const throttleOptions = { leading: true, trailing: true } | |
39 | ||
40 | const scrollObservable = fromEvent(this.container || window, 'scroll') | |
41 | .pipe( | |
42 | startWith(null), | |
43 | throttleTime(200, undefined, throttleOptions), | |
44 | map(() => this.getScrollInfo()), | |
45 | distinctUntilChanged((o1, o2) => o1.current === o2.current), | |
46 | share() | |
47 | ) | |
48 | ||
49 | // Scroll Down | |
50 | this.scrollDownSub = scrollObservable | |
51 | .pipe( | |
52 | // Check we scroll down | |
53 | filter(({ current }) => { | |
54 | const res = this.lastCurrentBottom < current | |
55 | ||
56 | this.lastCurrentBottom = current | |
57 | return res | |
58 | }), | |
59 | filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit) | |
60 | ) | |
61 | .subscribe(() => this.nearOfBottom.emit()) | |
62 | } | |
63 | ||
64 | private getScrollInfo () { | |
65 | if (this.container) { | |
66 | return { current: this.container.scrollTop, maximumScroll: this.container.scrollHeight } | |
67 | } | |
68 | ||
69 | return { current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight } | |
70 | } | |
71 | } |