minimal promise example

_promises.js

// bare minimum promise implementation
function promise() {
    // the promise caller will pass these along in `then`
    this.successFn = function() {};
    this.errorFn = function() {};
}

promise.prototype.resolve = function(result) {
    this.successFn(result);
};

promise.prototype.reject = function(error) {
    this.errorFn(error);
};

promise.prototype.catch = function(error) {
    this.errorFn(error);
};

promise.prototype.then = function(successHandler, errorHandler) {
    this.successFn = successHandler;
    this.errorFn = errorHandler;
};

// Example usage

// do async things with a promise
function myAsyncFnWithPromise() {
    // get our object with about 6 extra functions
    var deferredPromise = new promise();

    doSomethingAsyncWithCallbacks(function(err, res) {
        if (err) {
            return deferred.reject(err);
        }
        deferredPromise.resolve(res);
    });

    return deferredPromise;
}

myAsyncFnWithPromise().then(function(result) {
    console.log('wow isnt this great', result);
}, function(err) {
    console.error(err);
});

callbacks.js

// bare minimum plain callbacks implementation
// nothing, just write the dang function

// example usage

// do async things with a callback
function myAsyncFn(done) {
    doSomethingAsyncWithCallbacks(function(err, res) {
        done(err, res);
    });
    // or
    // doSomethingAsyncWithCallbacks(done);
}

myAsyncFn(function(err, result) {
    if (err) {
        throw err;
    }
    console.log('wow isnt this great', result);
});