Exciting release!Introducing "safe npm". Learn more
Log inDemoInstall


Package Overview
File Explorer

Advanced tools


utility to run functions when dom elements are visible


Version published
Weekly downloads
decreased by-9.4%

Weekly downloads



appear appear

Track the visibility of dom elements and fire user defined callbacks as they appear and disappear.


  • appear.js simple test page
  • appearlazy - a full fledged lazy image loader that uses appear.js

Be sure to view the documentation on the project page


Include appear.js in your page, it has no dependencies.

Call appear() passing in an object with the following:

  • init function to run when dom is interactive, but before appear.js has started tracking.
  • elements required function that returns an htmlcollection of elements to track. The dom will be interactive at this point. Can alternatively be an existing htmlcollection instead of a function.
  • appear function to run when an element is in view, passed the element that has come into view. If defined then appear.js will track elements until they come into view.
  • disappear function to run when an element goes out of view, passed the element that has gone out of view. If defined then appear.js will track elements until they go out of view.
  • reappear if true appear.js will keep tracking elements for successfuive appears and dissappears. Default is false.
  • bounds increase, in pixels, to the threshold size of the element so it can be "viewable" before it is actually in the viewport.
  • debounce appear.js tracks elements on browser scroll and resize, for performance reasons this check is "debounced" to only happen once for multiple events, 50ms after the last event ends. You can override this value here.
  • deltaSpeed in addition to debouncing, appear.js will also check for items during continuous slow scrolling, you can controll how slow the scrolling should be via this value. Default is 50 (pixels).
  • deltaTimeout after a succesful delta speed check, appear.js will not check for viewable items again until this timeout passes. Default is 500 (ms).
  • done function called when appear.js is no longer tracking any items and event listeners have been removed.


appear({ init: function init(){ console.log('dom is ready'); }, elements: function elements(){ // work with all elements with the class "track" return document.getElementsByClassName('track'); }, appear: function appear(el){ console.log('visible', el); }, disappear: function disappear(el){ console.log('no longer visible', el); }, bounds: 200, reappear: true });


appear() will return an object with the following:

  • trigger() force a check for viewable elements.
  • pause() temporarily stop tracking elements.
  • resume() resume tracking elements.
  • destroy() permanently stop tracking elements.


source or minified

appear.js logo designed by Magicon from the Noun Project :: Creative Commons - Attribution (CC BY 3.0)


Last updated on 03 Apr 2015

Did you know?

Socket installs a Github app to automatically flag issues on every pull request and report the health of your dependencies. Find out what is inside your node modules and prevent malicious activity before you update the dependencies.

Install Socket
support@socket.devSocket SOC 2 Logo


  • Package Issues
  • Integrations
  • Docs
  • Pricing
  • FAQ
  • Roadmap

Stay in touch

Get open source security insights delivered straight into your inbox.

  • Terms
  • Privacy
  • Security

Made with ⚡️ by Socket Inc