Promise.settle implementation

promise+settle.js

// ES6 version of settle
Promise.settle = function(promises) {
    function PromiseInspection(fulfilled, val) {
        return {
            isFulfilled: function() {
                return fulfilled;
            }, isRejected: function() {
                return !fulfilled;
            }, isPending: function() {
                // PromiseInspection objects created here are never pending
                return false;
            }, value: function() {
                if (!fulfilled) {
                    throw new Error("Can't call .value() on a promise that is not fulfilled");
                }
                return val;
            }, reason: function() {
                if (fulfilled) {
                    throw new Error("Can't call .reason() on a promise that is fulfilled");
                }
                return val;
            }
        };
    }

    return Promise.all(promises.map(function(p) {
        // make sure any values are wrapped in a promise
        if (!Promise.isPromise(p)) {
            p = Promise.resolve(p);
        }
        return p.then(function(val) {
            return new PromiseInspection(true, val);
        }, function(err) {
            return new PromiseInspection(false, err);
        });
    }));
}

see here.