simple-promise

gistfile1.js

var Promise = function (fun) {
    var me = this,
        resolve = function (val) {
            me.resolve(val);
        },
        reject = function (val) {
            me.reject(val);
        }
    me._st = 'pending';
    me._rsq = null;
    me._rjq = null;
    (typeof fun === 'function') && fun(resolve, reject);
},
fn = Promise.prototype;



fn.then = function (resolve, reject) {
    var pms = new Promise();
    this._rsq = function (val) {
        var ret = resolve ? resolve(val) : val;
        if (ret instanceof Promise) {
            ret.then(function (val) {
                pms.resolve(val);
            });
        }
        else{
            pms.resolve(ret);
        }
    };
    this._rjq = function (val) {
        pms.reject(reject(val));
    };
    return pms;
}
fn.catch = function (reject) {
    return this.then(null, reject);
}


fn.resolve = function (val) {
    if (this._st === 'resolved' || this._st === 'pending') {
        this._st = 'resolved';
        this._rsq && this._rsq(val);
    }
}

fn.reject = function (val) {
    if (this._st === 'rejected' || this._st === 'pending') {
        this._st = 'rejected';
        this._rsq && this._rjq(val);
    }
}

Promise.all = function (arr) {
    var pms = new Promise();
    var len = arr.length,
        i = 0,
        res = 0;
    while (i < len) {
        arr[i].then(
            function () {
                if (++res === len) {
                    pms.resolve();
                }
            },
            function (val) {
                pms.reject(val);
            }
        );
        i++;
    }
    return pms;
}

Promise.resolve = function (obj) {
    var pms = new Promise();
    if (obj && typeof obj.then === 'function') {
        for (var i in pms) {
            obj[i] = pms[i];
        }
        return obj;
    }
    else {
        setTimeout(function () {
            pms.resolve(obj);
        });
        return pms;
    }
}