Powerful application events and event handling, made easy.

npm install eventi
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Powerful application events and event handling, made easy.

Getting Started

Download the minified version or the development version. Build Status
Bower: bower install eventi
NPM: npm install eventi
Component: component install esha/Eventi


  • JavaScript development is ultimately event-based development.
  • Application events (aka custom events) are usually under-used or poorly-used in webapps.
  • Events are the best way to decouple modules and components without isolating them entirely.
  • DOM event bubbling, in particular, has much potential for meaningful event based interfaces.
  • Environment events get simple types and rich data, not the mushed-up 'nounVerbAdjective' types with poor data that most heavy custom event users end up using.
  • Custom events can be awesome, especially when you have rich features and patterns that are simple to use.
  • Declarative events are completely unsupported out there. This is a travesty.


  • A rich event platform that's easy to use and to extend.
  • A declarative syntax for working with rich, informative events.
  • DOM and object support
  • Handling for complex event types (combos, async sequences, singletons, etc).
  • Robust, error tolerant listener execution
  • Support for best-practices like "signals" (aka pre-defined types) and declarative event mapping
  • Lots of solid, maintainable test code
  • Impressive, interactive demo (ideas, anyone?)
  • Three versions (tall, grande, venti): tall is frame/core/fire/on, grande adds declare/singleton/key/location, venti adds off/until/combo/types
  • Venti is the default version to encourage much event-based awesomeness for everyone.
  • Grande includes basic webapp tools.
  • Tall could be enough for light server-side work.

Code Plans

Eventi.frame (useless on its own)

  • external IIFE
  • universal module definition
  • CustomEvent constructor polyfill
  • body is resolved to build tool specified (sub)set of the following content

core.js (not much use on its own)

  • rich event syntax parsing: Eventi("group:kind#label('val')") -> { category:'group', type:'kind', tags:['label'], label:true, detail:'val' }
  • parser should be extensible (for supporting jQuery namespaces or keyCodes or whatever)
  • detail can be resolvable reference, string, or limited json (no parentheses)
  • interface sharing (pass this as target param to copied functions): Eventi.fy(foo) -> foo.fire('type')
  • add stopImmediatePropagation and immediatePropagationStopped to event interface

on.js (requires core.js)

  • simple event registration: Eventi.on([target, ]'type', fn)
  • space delimited multiple registration: Eventi.on([target, ]'first second third', fn)
  • filter by category and/or tag: Eventi.on([target, ]"category:type#tag", fn)
  • bind data w/listener: Eventi.on([target, ]'type', fn, data)
  • applying rich event data as listener arg(s): Eventi.on([target, ]'type', function(e, arg, arg){})
  • implementation: one listener per target that gets registered for every handled type. the listener handles each event by looking amongst its handlers for those that match the event and executing them

fire.js (requires core.js, uses on.js)

  • object or DOM custom event dispatch: Eventi.fire(Node|object, 'type')
  • handler errors caught and thrown in next tick to avoid interrupting sibling handlers or hiding errors
  • implicit global target: Eventi.fire('type') === `Eventi.fire(document || this, 'type')
  • multiple target specification: Eventi.fire(Array|NodeList, 'type')
  • fire with handler arguments Eventi.fire([target, ]'type', data)
  • TODO: consider non-DOM propagation when typeof object.parent === "object"

delegate.js (requires on.js)

  • alias Element.prototype.matches from the prefixed matchesSelector versions
  • filter by selector (aka delegation): Eventi.on([target, ]'type<.selector>', fn)

declare.js (requires on.js and fire.js)

  • declare data-eventi="submit /beforeunload=quit" on a root or container element
  • declare specific responses on descendent(s): submit="validate>save" quit="Utils.persist"
  • try to resolve attr values at call-time to either element or global function (declared event handler)
  • otherwise, fire as application event (declared event mapping)
  • impl should scan document for data-eventi attributes on DOMContentLoaded, register those listeners
  • click="..." is globally supported by default using trigger.js' intelligent click/enter logic

singleton.js (requires fire.js and on.js)

  • singleton events (immediately call late listeners, ignore multiple firings)
  • "listen" for them: Eventi.on([target, ]'^type', fn)
  • fire them so they're remembered: Eventi.fire([target, ]'^type', fn)
  • alias DOMContentLoaded to '^ready'

key.js (requires on.js)

  • filter key events: Eventi.on([target, ]'keyup[shift-a]', fn)

location.js (requires on.js and fire.js)

  • event-based routing: Eventi.on('location@?view={view}', function(e, url, params){ console.log(params.view); })
  • event-based history.pushState: Eventi.fire('location@?view={0}', ['foo'])
  • consistent event for all popstate/hashchange/pushstate changes: Eventi.on('location', function(e){ console.log(e.location, e.oldLocation, e.srcEvent); })

off.js (requires on.js)

  • simple listener removal: Eventi.off([target, ]['type', ][fn])
  • multiple removal: Eventi.off([target, ]['first second third', ][fn])
  • remove by category and/or tag: Eventi.off([target, ]['category:type#tag', ][fn])

end.js (requires on.js)

  • this will remove handlers once the specified condition is satisfied
  • number of executions: Eventi.on([target, ]'type$3', fn)
  • test ref for truthiness: Eventi.on([target, ]'type$reference', fn)
  • call function for truthiness: Eventi.on([target, ]'type$test.fn', fn)

sequence.js (requires fire.js)

  • fire controllable sequence of events: Eventi.fire([target, ]'first,second'[, data...])
  • event sequence firing controls (w/async support via promises): e.pauseSequence([promise]),e.resumeSequence(), e.isSequencePaused()

combo.js (requires on.js and off.js)

  • combo events (call after all specified events, then reset): Eventi.on([target, ]'foo+bar', fn)
  • event sequences (ordered combos): Eventi.on([target, ]'one,two,three', fn...)
  • configurable timeout for combo events: Eventi.on([target, ]'one,two', fn, 1000)

alias.js (requires core and declare.js)

  • provide both global and local type specification with minimal API
  • global: Eventi.alias('type'); -> Eventi.on.type([target, ]handler)
  • local (after Eventi.fy(o)): Eventi.alias(o, 'type', 'type2') -> target.until.type2(1, handler)
  • obviously, aliases cannot have the same name as Function properties like 'call' or 'length'


  • documentation
  • demo app/site
  • integrations (jQuery, Visual Event 2, Capo, etc)
  • consider limited grouping syntax for types with partial overlap: group:{type#tag other$1}#tag2 but probably don't bother due to incompatibility w/aliasing and current parsing
  • consider wildcard * syntax, to require a match field presence instead of equality, or possibly partial equality. but resist doing it, as this could get out of hand...

Plan for jquery.eventi.js

  • add custom properties to $.event.props
  • add namespace support to rich syntax (ick)
  • listen for events in jQuery's manual bubbling system (ick again)
  • wrap $.fn.trigger, $.fn.on, $.fn.off, and maybe $.fn.one to intercept calls with Eventi syntax


Release History

  • 2014-02-11 v0.5.0 (alpha)
  • 2014-04-03 v1.0.0 (beta)
  • 2014-04-04 v1.0.1 (beta - IE fixes)
  • 2014-04-09 v1.0.2 (beta - toString and location fix)
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