intersection_observer 1.0.0

  • Example
  • Installing
  • Versions
  • 27


A Dart wrapper for the Intersection Observer API


import 'dart:html';
import "package:js/js.dart";
import 'package:intersection_observer/intersection_observer.dart' as io;

void main() {
  Element output = querySelector('#output');
  var blocks = querySelectorAll('.block');
  for (var b in blocks) {
  io.IntersectionObserverCallback callback = (List<io.IntersectionObserverEntry> entries,
      io.IntersectionObserver observer) {
    entries.forEach((io.IntersectionObserverEntry entry) {'intersecting', entry.isIntersecting.toString());

      // print('''
      // boundingClientRect: ${entry.boundingClientRect}
      // intersectionRatio: ${entry.intersectionRatio}
      // intersectionRect: ${entry.intersectionRect}
      // isIntersecting: ${entry.isIntersecting}
      // rootBounds: ${entry.rootBounds}
      // target: ${}
      // time: ${entry.time}

      // observer.root ${observer.root}
      // observer.rootMargin ${observer.rootMargin}
      // observer.thresholds ${observer.thresholds}
      // ''');
    var redInView = blocks.where((Element el) => el.getAttribute('intersecting') == 'true' && el.classes.contains('red')).length;
    var greenInView = blocks.where((Element el) => el.getAttribute('intersecting') == 'true' && el.classes.contains('green')).length;
    output.innerHtml = '${redInView} red blocks in view <br> ${greenInView} green blocks in view';
  io.IntersectionObserver observer = new io.IntersectionObserver(callback);
  querySelectorAll('.block').forEach((Element el) {

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:

  intersection_observer: "^1.0.0"

2. Install it

You can install packages from the command line:

with pub:

$ pub get

Alternatively, your editor might support pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

      import 'package:intersection_observer/intersection_observer.dart';
Version Uploaded Documentation Archive
1.0.0 Oct 27, 2017 Go to the documentation of intersection_observer 1.0.0 Download intersection_observer 1.0.0 archive


We analyzed this package on Jun 12, 2018, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.0.0-dev.60.0
  • pana: 0.11.3


Describes how popular the package is relative to other packages. [more]
0 / 100
Code health derived from static analysis. [more]
37 / 100
Reflects how tidy and up-to-date the package is. [more]
79 / 100
Overall score:
Weighted score of the above. [more]
Learn more about scoring.


Detected platforms: web

Primary library: package:intersection_observer/intersection_observer.dart with components: html, js.


  • Maintain

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  • Fix analysis and formatting issues.

    Analysis or formatting checks reported 7 warnings 1 hint.

    Strong-mode analysis of lib/intersection_observer.dart gave the following warning:

    line: 63 col: 19
    The final variable 'boundingClientRect' must be initialized.

  • The description is too short.

    Add more detail about the package, what it does and what is its target use case. Try to write at least 60 characters.


Package Constraint Resolved Available
Direct dependencies
Dart SDK >=1.22.1 <2.0.0
js ^0.6.1 0.6.1
Dev dependencies
browser ^0.10.0