promise.js

(function (root, factory) {
  if (typeof define === 'function' && define.amd) {
    define([], factory);
  } else if (typeof exports === 'object') {
    module.exports = factory();
  } else {
    root.Promise = factory();
  }
}(this, function () {
  function Promise(init) {
    var state = -1, queue = [], value;
    function fulfill(state, value, handler) {
      if(state < 0) {return;}
      while(handler=queue.pop()) handler[state](value);
    }
    function resolve(val) {
      state < 0 && fulfill(state=0,value=val);
    }
    function reject(val) {
      state < 0 && fulfill(state=1,value=val);
    }
    function handle(handler, res, rej) {
      return function(val) {
        if(handler){
          try {val = handler(value)}
          catch(e){return rej(e);}
        }
        if (val && val.then) { return val.then(res, rej) }
        state > 0 ? rej(val) : res(val)
      };
    }
    this.then = function(success, fail) {
      return new Promise(function(res, rej) {
        queue.push([handle(success, res, rej),handle(fail, res, rej)])
        fulfill(state, value);
      });
    };
    init(resolve, reject);
  }
  Promise.prototype.catch = function(fail) {
    return this.then(null, fail);
  };
  Promise.resolve = function(promise) {
    if(promise instanceof Promise) {return promise}
    return new Promise(function(resolve, reject) {
      promise && promise.then 
      ? promise.then(resolve, reject)
      : promise instanceof Error 
        ? reject(promise)
        : resolve(promise)
    })
  }
  Promise.defer = function() {
    var defer = {};
    defer.promise = new Promise(function(resolve, reject) {
      defer.resolve = resolve;
      defer.reject = reject;
    })
    return defer;
  };
  Promise.all = function(array) {
    var result = [];
    return new Promise(function(resolve, reject) {
      if(!array.length) {resolve(result); }
      function accumulate(value) { result.push(value) === array.length && resolve(result);}
      array.forEach(function(promise) {Promise.resolve(promise).then(accumulate, reject);});
    });
  };
  return Promise;
}));