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LinkedIn's JavaScript viewport tracking library and IntersectionObserver polyfill
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Spaniel Build Status npm version

LinkedIn's JavaScript viewport tracking library and IntersectionObserver polyfill. Track what the user actually sees.

import { IntersectionObserver } from 'spaniel';

new IntersectionObserver((entries) => { console.log('I see you') }, {
  threshold: 0.5

Practical uses included:

  • Determining advertisement impressions
  • Impression discounting feedback for relevance systems
  • Occlusion culling - Don't render an object until user is close to scrolling the object into the viewport

Usage and API Docs

Spaniel provides additional abstractions on top of IntersectionObserver, provides APIs for hooking into the low-level internals, and has some limitations as a non-complete polyfill. Learn more by reading the Usage and API Docs.

Why use Spaniel?

  • Provides the future-proofing of a WCIG API, but with an expanded feature-set built upon said API.
  • Tested and iterated upon in production by LinkedIn since late 2014
  • Highly performant, only relies on requestAnimationFrame
  • Extensive requestAnmiationFrame task/utility API

How is it tested?

Spaniel has both unit tests and a headless test suite. The headless tests are run using Nightmare.

How big is Spaniel?

Checkout size.txt to see the current minified UMD gzipped size.

You can also run npm run stats to measure locally.


Spaniel is a standard NPM/CommonJS module. You can use a build tool like browserify or webpack to include Spaniel in your application.

If you're using rollup, an ES6 version is built at /exports/es6/spaniel.js (as noted by jsnext:main in package.json).

Alternatively, running npm run build will generate a UMD file at /exports/spaniel.js, and a minified UMD file at /exports/min/spaniel.js. You can use the minified file in production.

Development setup

The Spaniel source code is written in TypeScript.

You will need testem installed globally to run the tests.

npm install -g testem

You will also need to install phantom.js globally.

// Install dependencies
npm install

// Run build
npm run build

// Watch and auto-rebuild
npm run watch

// Serve test app
npm run serve

// Run the tests
npm run test

IntersectionObserver Resources


Copyright 2017 LinkedIn Corp. All rights reserved.

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