Promise pattern

promise.coffee

class Promise
    then: (@onResolved, @onRejected) ->
        return

    resolve: (val) ->
        @onResolved val
        return

    reject: (err) ->
        @onRejected err
        return


ajax = (url) ->
    xhr = new XMLHttpRequest
    promise = new Promise
    xhr.open 'GET', url, true
    xhr.onload = (e) ->
        if @status is 200
            result = JSON.parse @responseText
            promise.resolve result
        return

    xhr.onerror = (e) ->
        promise.reject e

    xhr.send()

    return promise

onResolved = (val) ->
    console.log val

onReject = (err) ->
    console.log err.message

ajax('http://...').then onResolved, onReject