This project is basically a modified version of sdecima/javascript-detect-element-resize including these changes:

• Try to utilize native ResizeObserver first.
• Adopt Mutation-based approach to track detaching/attaching in both DOM trees and render trees (see que-etc/resize-observer-polyfill).
• Use ES Modules.
• Put most CSS content inside a separate .css file.
• Drop support for IE8 and below.
• Make the package available from npm.

$ npm i --save resize-detector

import { addListener, removeListener } from 'resize-detector'

// adding listener
addListener(elem, callback)

// removing listener, callback can be omitted to indicate that
// all event listeners should be removed
removeListener(elem, callback)

this inside callback function is the element whose size has been changed, also callback receive element as first argument.

As resize-detector is published in both ES Module & CommonJS format and when you use webpack to bundle your app, the ESM version will be imported. It is not transpiled by Babel or similar tools so you have to transpile it in your build process.

For webpack with babe-loader you need to add it to the include field of the options:

// ...
{
  test: /\.js$/,
  loader: 'babel-loader',
  include: [
    // other stuff to be transpiled
    // ...
    path.resolve('node_modules/resize-detector')
  ]
}
// ...

If you are using other toolchain, just configure your bundler similarly so that resize-detector will be transpiled during build process.

• Is polyfill?

  No.

• Native first

  Yes.

• Strategy

  Scroll-based + Mutation-based.

• Pros

  • Small size.
  • Minimal limitations.

• Side effects

  • Targets with position: static will become position: relative.
  • Several hidden elements will be injected into the target elements.

• Is polyfill?

  No.

• Native first

  No.

• Strategy

  Scroll-based.

• Pros

  • Small size.
  • Higher performance comparing to hidden <object>s.
  • Compatible with down to IE7.

• Side effects

  • Targets with position: static will become position: relative.
  • Several hidden elements will be injected into the target elements.

• Limitations

  • Cannot track detach/attach or visibility change on IE10 and below.

• Is polyfill

  Yes.

• Native first

  Yes.

• Fallback Strategy

  Use MutationObserver to observe every mutation in a document. For IE9/10, use Mutation Events instead.

• Pros

  • Small size.
  • Minimal side effects on target elements.
  • Can track detaching/attaching in both DOM trees and render trees as soon as it's triggered by DOM mutation.

• Limitations

  • Need extra transition event handling to catch size change from user interaction pseudo classes like :hover.
  • Delayed transitions will receive only one notification with the latest dimensions of an element.

• Is polyfill

  No.

• Native first

  No.

• Strategy

  Listen to resize events via hidden <iframe>s.

• Pros

  Dead simple.

• Side effects

  • Targets with position: static will become position: relative.
  • Several hidden elements will be injected into the target elements.
  • Relatively low performance.

• Limitations

  • Inapplicable for void elements.
  • Cannot track detach/attach or visibility change.

• Is polyfill?

  Yes.

• Native first

  Yes.

• Fallback Strategy

  Long polling through requestAnimationFrame or setTimeout.

• Pros

  Dead simple.

• Side effects

  • Might be not so performant by checking rendered sizes in each animation frame.

• Is polyfill?

  No.

• Native first

  No.

• Strategy

  Either hidden <object>s or scroll-based.

• Pros

  Two approaches available (Really, why?) with scroll-based approach being much faster than hidden <object>s.

• Side effects

  • Targets with position: static will become position: relative.
  • Several hidden elements will be injected into the target elements.

• Limitations

  • Package size is relatively large.
  • Inapplicable for void elements.
  • Cannot track detach/attach or visibility change.