finally.js

"use strict";
module.exports = function(Promise, NEXT_FILTER, tryConvertToPromise) {
var util = require("./util.js");
var wrapsPrimitiveReceiver = util.wrapsPrimitiveReceiver;
var isPrimitive = util.isPrimitive;
var thrower = util.thrower;

function returnThis() {
    return this;
}
function throwThis() {
    throw this;
}
function return$(r) {
    return function() {
        return r;
    };
}
function throw$(r) {
    return function() {
        throw r;
    };
}
function promisedFinally(ret, reasonOrValue, isFulfilled) {
    var then;
    if (wrapsPrimitiveReceiver && isPrimitive(reasonOrValue)) {
        then = isFulfilled ? return$(reasonOrValue) : throw$(reasonOrValue);
    } else {
        then = isFulfilled ? returnThis : throwThis;
    }
    return ret._then(then, thrower, undefined, reasonOrValue, undefined);
}

function finallyHandler(reasonOrValue) {
    var promise = this.promise;
    var handler = this.handler;

    var ret = promise._isBound()
                    ? handler.call(promise._boundTo)
                    : handler();

    if (ret !== undefined) {
        var maybePromise = tryConvertToPromise(ret, promise);
        if (maybePromise instanceof Promise) {
            maybePromise = maybePromise._target();
            return promisedFinally(maybePromise, reasonOrValue,
                                    promise.isFulfilled());
        }
    }

    if (promise.isRejected()) {
        NEXT_FILTER.e = reasonOrValue;
        return NEXT_FILTER;
    } else {
        return reasonOrValue;
    }
}

function tapHandler(value) {
    var promise = this.promise;
    var handler = this.handler;

    var ret = promise._isBound()
                    ? handler.call(promise._boundTo, value)
                    : handler(value);

    if (ret !== undefined) {
        var maybePromise = tryConvertToPromise(ret, promise);
        if (maybePromise instanceof Promise) {
            maybePromise = maybePromise._target();
            return promisedFinally(maybePromise, value, true);
        }
    }
    return value;
}

Promise.prototype._passThroughHandler = function (handler, isFinally) {
    if (typeof handler !== "function") return this.then();

    var promiseAndHandler = {
        promise: this,
        handler: handler
    };

    return this._then(
            isFinally ? finallyHandler : tapHandler,
            isFinally ? finallyHandler : undefined, undefined,
            promiseAndHandler, undefined);
};

Promise.prototype.lastly =
Promise.prototype["finally"] = function (handler) {
    return this._passThroughHandler(handler, true);
};

Promise.prototype.tap = function (handler) {
    return this._passThroughHandler(handler, false);
};
};