A small extension to the Promises interface for ES6.
Extends the Promise object with a first function that takes an array of promises/functions as argument. The promises are then executed sequentially starting at index 0. Returns a promise that resolves with the result of the first resolving promise in the array of promises provided, or rejects if none of the promises resolves.
To get started, simply require('index.js'); and Promise will be extended with a first function. If you do not want to extend the Promise interface, you can require('/lib/promise-chain.js') and use the provided first function.
With Promises:
Promise.first([p1, p2])
.then(function(data) {
// p1 or p2 resolved with data
}, function() {
// neither p1 nor p2 resolved
});
With functions:
Promise.first([func1, func2])
.then(function(data) {
// func1 or func2 returned a promise that resolved with data
}, function() {
// neither func1 nor func2 returned a promise that resolved
});
Mixed:
Promise.first([p1, func1])
.then(function(data) {
// p1 resolved, or func1 returned a promise that resolved with data
}, function() {
// neither p1 nor return value of func1 resolved
});