Barebone Promise/A+ implementation.

• Extremely small (~ 1kb minified), extremely fast

• .then() being asynchronous is optional.

• Passing the Promises/A+ Compliance Test Suite

npm install promise-now

var Promise = require('promise-now');
var promise = new Promise();

promise.then(addOne).then(addOne).then(function(num) {
	console.log(num); // 3
});
promise.fulfill(1);

function addOne(num) {
	return num + 1;
}

Call fulfillCallack(value) if promise is fulfilled with value.

Or call rejectCallback(reason) if promise is rejected with reason.

Return a new promise.

Fulfill promise with value. this keyword equals to context in callbacks if provided.

Return original promise.

Reject promise with reason. this keyword equals to context in callbacks if provided.

Return original promise.

Like .then(), but throw with reason (asynchronously) if promise is rejected. Should be called at the end of .then() chain.

Return undefined.

If you can be sure that you will never write code like:

var promise = new Promise().fulfill();

promise.then(function() {
	console.log(2);
});
console.log(1);

In other words, you will not put synchronous code after asynchronous function calls, then it doesn't make a difference if .then() is asynchronous or not.

By default, promise-now use synchronous .then(). If you need the asynchronous version, simply patch promise-now (see test/promise.js on how it's done).