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node_modules/ee-first/index.js 1.64 KB
aaac7fed   liuqimichale   add
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  /*!
   * ee-first
   * Copyright(c) 2014 Jonathan Ong
   * MIT Licensed
   */
  
  'use strict'
  
  /**
   * Module exports.
   * @public
   */
  
  module.exports = first
  
  /**
   * Get the first event in a set of event emitters and event pairs.
   *
   * @param {array} stuff
   * @param {function} done
   * @public
   */
  
  function first(stuff, done) {
    if (!Array.isArray(stuff))
      throw new TypeError('arg must be an array of [ee, events...] arrays')
  
    var cleanups = []
  
    for (var i = 0; i < stuff.length; i++) {
      var arr = stuff[i]
  
      if (!Array.isArray(arr) || arr.length < 2)
        throw new TypeError('each array member must be [ee, events...]')
  
      var ee = arr[0]
  
      for (var j = 1; j < arr.length; j++) {
        var event = arr[j]
        var fn = listener(event, callback)
  
        // listen to the event
        ee.on(event, fn)
        // push this listener to the list of cleanups
        cleanups.push({
          ee: ee,
          event: event,
          fn: fn,
        })
      }
    }
  
    function callback() {
      cleanup()
      done.apply(null, arguments)
    }
  
    function cleanup() {
      var x
      for (var i = 0; i < cleanups.length; i++) {
        x = cleanups[i]
        x.ee.removeListener(x.event, x.fn)
      }
    }
  
    function thunk(fn) {
      done = fn
    }
  
    thunk.cancel = cleanup
  
    return thunk
  }
  
  /**
   * Create the event listener.
   * @private
   */
  
  function listener(event, done) {
    return function onevent(arg1) {
      var args = new Array(arguments.length)
      var ee = this
      var err = event === 'error'
        ? arg1
        : null
  
      // copy args to prevent arguments escaping scope
      for (var i = 0; i < args.length; i++) {
        args[i] = arguments[i]
      }
  
      done(err, ee, event, args)
    }
  }