eventemitter2

Postconditions — what we check

• EventEmitter2 · eventemitter2-001

  error
  Whenerror event emitted without listener
  ThrowsUncaught exception unless ignoreErrors configured
  Required handlingCaller MUST attach error event listener
  costmediumin prodimmediate exceptionusers seeservice unavailablevisibilityvisible
  Sources[1]
• emit · eventemitter2-emit-unhandled-error

  error
  Whenerror event emitted with no listener and ignoreErrors: false (default)
  ThrowsError — either re-throws the emitted Error instance or throws new Error("Uncaught, unspecified 'error' event.")
  Required handlingCaller MUST attach .on('error', handler) before emitting error events, or pass ignoreErrors:true to the constructor
  costmediumin prodimmediate exceptionusers seeservice unavailablevisibilityvisible
  Sources[2]
• emitAsync · eventemitter2-emit-async-unhandled-error

  error
  WhenemitAsync('error', err) called with no 'error' listener registered and ignoreErrors: false
  ThrowsReturns Promise.reject(err) — a rejected Promise with the error or a string message
  Required handlingCaller MUST attach .on('error', handler) OR wrap emitAsync() in try/catch or .catch()
  costmediumin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• emitAsync · eventemitter2-emit-async-listener-rejection

  warning
  Whenany registered listener throws or returns a rejected Promise
  ThrowsReturns rejected Promise with the first listener's rejection reason (Promise.all semantics)
  Required handlingCaller MUST await emitAsync() and wrap in try/catch, or chain .catch()
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2][3]
• waitFor · eventemitter2-wait-for-timeout

  warning
  Whentimeout option is > 0 and the event is not emitted within that duration
  ThrowsRejects with Error('timeout') — the rejection message is literally 'timeout'
  Required handlingCaller MUST wrap waitFor() in try/catch or .catch() when using timeout option
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• waitFor · eventemitter2-wait-for-cancel

  warning
  Whenpromise.cancel() is called before the event fires
  ThrowsRejects with Error('canceled')
  Required handlingCaller MUST handle rejection if cancel() can be called on in-flight promises
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• waitFor · eventemitter2-wait-for-handle-error

  warning
  WhenhandleError: true in options AND the event fires with a truthy first argument
  ThrowsRejects with the first argument as the error reason
  Required handlingCaller MUST wrap in try/catch when handleError option is enabled
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2][4]
• EventEmitter2.once · eventemitter2-static-once-error-rejection

  error
  Whenthe emitter emits 'error' before the target event fires
  ThrowsRejects with the error emitted — the rejection reason is the Error object from the error event
  Required handlingCaller MUST wrap EventEmitter2.once() in try/catch or chain .catch()
  costmediumin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• EventEmitter2.once · eventemitter2-static-once-timeout

  warning
  Whentimeout option is > 0 and the event does not fire within that duration
  ThrowsRejects with Error('timeout')
  Required handlingCaller MUST wrap in try/catch or .catch() when using timeout option
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• EventEmitter2.once · eventemitter2-static-once-cancel

  warning
  Whenpromise.cancel() is called before the event fires
  ThrowsRejects with Error('canceled')
  Required handlingCaller MUST handle rejection if cancel() can be called on in-flight promises
  costlowin proddelayed failureusers seedegraded performancevisibilitysilent
  Sources[2]
• listenTo · eventemitter2-listen-to-invalid-target

  error
  Whentarget parameter is not an object, or target does not implement addEventListener/on/addListener
  ThrowsTypeError('target musts be an object') or Error('target does not implement any known event API')
  Required handlingCaller MUST validate target implements an event API before calling listenTo()
  costlowin prodimmediate exceptionusers seeservice unavailablevisibilityvisible
  Sources[2]
• listenTo · eventemitter2-listen-to-invalid-options

  warning
  Whenoptions.on or options.off are provided but are not functions
  ThrowsTypeError('on method must be a function') or TypeError('off method must be a function')
  Required handlingCaller MUST ensure on/off hooks in options are valid functions when using custom subscription API
  costlowin prodimmediate exceptionusers seeservice unavailablevisibilityvisible
  Sources[2]

Sources

Every postcondition cites at least one of these. Numbered to match the footnotes above.

1. [1]github.com/EventEmitter2/EventEmitter2https://github.com/EventEmitter2/EventEmitter2
2. [2]github.com/EventEmitter2/EventEmitter2https://github.com/EventEmitter2/EventEmitter2/blob/master/lib/eventemitter2.js
3. [3]developer.mozilla.org/en-US/docshttps://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all
4. [4]github.com/EventEmitter2/EventEmitter2https://github.com/EventEmitter2/EventEmitter2/blob/master/README.md