PROJECT NO LONGER MAINTAINED

Please use native intersection-observer to achieve similar results

ngx-scroll-tracker

Track any element to enhance scroll-based features in you app.
Works for Angular 4+, both AoT and SSR.

Installation

$ npm install @nicky-lenaers/ngx-scroll-tracker

Usage

1. Import the Angular Module

import { NgModule } from '@angular/core';
import { ScrollTrackerModule } from '@nicky-lenaers/ngx-scroll-tracker';

@NgModule({
  imports: [
    ...
    ScrollTrackerModule.forRoot()
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

2. Apply Angular Directive

...
<div (ngx-scroll-tracker)="handler($event)">
  <h1>Lorem Ipsum</h1>
  <p>Dolor sit amet</p>
</div>

3. Handle Scroll Tracker Events

import { Component } from '@angular/core';
import { ScrollTrackerEventData } from '@nicky-lenaers/ngx-scroll-tracker';

@Component({})
export class MyComponent {

  public handler(eventData: ScrollTrackerEventData) {
    // Use the eventData!
  }
}

Data API

The ScrollTrackerEventData interface defines the data being emitted from the tracker. First-level properties:

Property	Description
$event	Native Browser Event
elementRef	Angular ElementRef to tracked Element
data	The scroll data for the Element

The data property holds the following properties:

Property	Description
elementTop.fromContainerTop	Distance between the top of the tracked element and the top of its scrollable container (pixels and ratio)
elementTop.fromContainerBottom	Distance between the top of the tracked element and the bottom of its scrollable container (pixels and ratio)
elementBottom.fromContainerTop	Distance between the bottom of the tracked element and the top of its scrollable container (pixels and ratio)
elementBottom.fromContainerBottom	Distance between the bottom of the tracked element and the bottom of its scrollable container (pixels and ratio)

Notes

• Negative values for both pixels and ratio means the element has scrolled past its contianer treshold (.fromContainerTop etc.).
• Positive values for both pixels and ratio means the element has not yet reached its container tresheld.

Example

import { Component } from '@angular/core';
import { ScrollTrackerEventData } from '@nicky-lenaers/ngx-scroll-tracker';

@Component({})
export class MyComponent {

  public handler(eventData: ScrollTrackerEventData) {

    if (eventData.data.elementTop.fromContainerTop.ratio < 0) {
      console.log('Element Top is past Containter Top');
    }
    if (eventData.data.elementBottom.fromContainerBottom.ratio < 0) {
      console.log('Element Bottom is past Containter Bottom');
    }
    if (eventData.data.elementTop.fromContainerTop.pixels < 200) {
      console.log('Element Top is 200px from Containter Top');
    }
    if (eventData.data.elementTop.fromContainerTop.ratio > 0.25) {
      console.log('Element Top is past Containter Top');
    }

  }
}

License

MIT