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14aa8556 | 1 | import { distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators' |
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2 | import { AfterContentChecked, Directive, ElementRef, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core' |
3 | import { fromEvent, Observable, Subscription } from 'rxjs' | |
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4 | |
5 | @Directive({ | |
6 | selector: '[myInfiniteScroller]' | |
7 | }) | |
ad453580 | 8 | export class InfiniteScrollerDirective implements OnInit, OnDestroy, AfterContentChecked { |
0cd4344f | 9 | @Input() percentLimit = 70 |
aa55a4da | 10 | @Input() autoInit = false |
bce47964 | 11 | @Input() onItself = false |
ad453580 | 12 | @Input() dataObservable: Observable<any[]> |
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13 | |
14 | @Output() nearOfBottom = new EventEmitter<void>() | |
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15 | |
16 | private decimalLimit = 0 | |
17 | private lastCurrentBottom = -1 | |
9af61e84 | 18 | private scrollDownSub: Subscription |
bce47964 | 19 | private container: HTMLElement |
0cd4344f | 20 | |
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21 | private checkScroll = false |
22 | ||
bce47964 | 23 | constructor (private el: ElementRef) { |
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24 | this.decimalLimit = this.percentLimit / 100 |
25 | } | |
26 | ||
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27 | ngAfterContentChecked () { |
28 | if (this.checkScroll) { | |
29 | this.checkScroll = false | |
30 | ||
31 | console.log('Checking if the initial state has a scroll.') | |
32 | ||
33 | if (this.hasScroll() === false) this.nearOfBottom.emit() | |
34 | } | |
35 | } | |
36 | ||
0cd4344f | 37 | ngOnInit () { |
aa55a4da | 38 | if (this.autoInit === true) return this.initialize() |
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39 | } |
40 | ||
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41 | ngOnDestroy () { |
42 | if (this.scrollDownSub) this.scrollDownSub.unsubscribe() | |
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43 | } |
44 | ||
0cd4344f | 45 | initialize () { |
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46 | this.container = this.onItself |
47 | ? this.el.nativeElement | |
48 | : document.documentElement | |
bce47964 | 49 | |
6a6d92b1 | 50 | // Emit the last value |
2c6bbd97 | 51 | const throttleOptions = { leading: true, trailing: true } |
6a6d92b1 | 52 | |
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53 | const scrollableElement = this.onItself ? this.container : window |
54 | const scrollObservable = fromEvent(scrollableElement, 'scroll') | |
db400f44 | 55 | .pipe( |
14aa8556 | 56 | startWith(true), |
db400f44 | 57 | throttleTime(200, undefined, throttleOptions), |
bce47964 | 58 | map(() => this.getScrollInfo()), |
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59 | distinctUntilChanged((o1, o2) => o1.current === o2.current), |
60 | share() | |
61 | ) | |
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62 | |
63 | // Scroll Down | |
9af61e84 | 64 | this.scrollDownSub = scrollObservable |
db400f44 | 65 | .pipe( |
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66 | filter(({ current }) => this.isScrollingDown(current)), |
67 | filter(({ current, maximumScroll }) => (current / maximumScroll) > this.decimalLimit) | |
db400f44 | 68 | ) |
0cd4344f | 69 | .subscribe(() => this.nearOfBottom.emit()) |
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70 | |
71 | if (this.dataObservable) { | |
72 | this.dataObservable | |
73 | .pipe(filter(d => d.length !== 0)) | |
74 | .subscribe(() => this.checkScroll = true) | |
75 | } | |
6a6d92b1 | 76 | } |
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77 | |
78 | private getScrollInfo () { | |
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79 | return { current: this.container.scrollTop, maximumScroll: this.getMaximumScroll() } |
80 | } | |
81 | ||
82 | private getMaximumScroll () { | |
83 | return this.container.scrollHeight - window.innerHeight | |
84 | } | |
85 | ||
86 | private hasScroll () { | |
87 | return this.getMaximumScroll() > 0 | |
88 | } | |
89 | ||
90 | private isScrollingDown (current: number) { | |
91 | const result = this.lastCurrentBottom < current | |
bce47964 | 92 | |
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93 | this.lastCurrentBottom = current |
94 | return result | |
bce47964 | 95 | } |
0cd4344f | 96 | } |