onmount

Run something when a DOM element appears and when it exits.
No dependencies. Legacy IE compatible. 1kb .min.gz.

Status

Overview

Detecting elements

Run something to initialize an element on its first appearance.

onmount = require('onmount')

onmount('.push-button', function () {
  $(this).on('click', function () {
    alert('working...')
  })
})

Polling for changes

Call $.onmount() everytime your code changes. →

$('<button class="push-button">Do something</button>')
  .appendTo('body')

$.onmount()

$(".push-button").click()  //=> 'working...'

jQuery integration

jQuery is optional; use it to poll on popular events. →

$(document).on('ready show.bs closed.bs load page:change', function () {
  $.onmount()
})

Cleanups

Supply a 2nd function to onmount() to execute something when the node is first detached. →

$.onmount('.push-button', function () {
  /*...*/
}, function () {
  alert('button was removed')
})

document.body.innerHTML = ''

$.onmount() //=> 'button was removed'

What for?

Onmount is a safe, reliable, idempotent, and testable way to attach JavaScript behaviors to DOM nodes. It's great for common websites that are not Single-Page Apps. Read more on its premise and motivation.

rsjs (Reasonable System for JavaScript Structure) is a great standard that onmount fits perfectly into.

Usage

Onmount is available via npm and Bower.

npm install onmount
bower install onmount

Usage info

It can be used as a CommonJS module or on its own. It doesn't require jQuery, but if jQuery is found, it'll attach itself to it as $.onmount.

onmount = require('onmount')    // With CommonJS (ie, Browserify)
window.onmount                  // with no module loaders:
$.onmount                       // with jQuery

API

onmount()

Runs all behaviors.

When used with jQuery, this can be passed as an event handler, eg, $(onmount) or $(document).on('load', onmount).

onmount(selector)

Runs all behaviors registered for selector.

onmount(selector, init())

Registers a behavior for selector to run the callback init().

onmount(selector, init(b), exit(b))

Registers a behavior for selector to run the callback init(). The exit() callback will be called once the behavior is triggered again but the element is no longer attached to the DOM.

The callbacks are passed an object b, and the same object is passed for both init and exit. This allows them to communicate and keep aware of state. A string ID is also provided, b.id, which is guaranteed unique for every behavior-element pair.

onmount.reset()

Clears all defined behaviors. Useful for tests.

onmount.observe()

Automatically invoke when new DOM elements appear using MutationObserver API. Returns true if it succeeds.

onmount.unobserve()

Turns off observation previously turned on via onmount.observe().

onmount.debug

Set this to true to see debug messages.

Browser compatibility

All modern browsers and IE8+. For legacy IE, use it with jQuery 1.x. Try the test suite in your browser. Try it with jQuery 1.x for legacy browsers.

Examples

Examples are available in the source repo. See examples →

Thanks

onmount © 2015+, Rico Sta. Cruz. Released under the MIT License.
Authored and maintained by Rico Sta. Cruz with help from contributors (list).

ricostacruz.com  ·  GitHub @rstacruz  ·  Twitter @rstacruz

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