Bluefeather

A collection of Promise utilities.

• Utility functions
  • delay
  • map
  • mapSeries
  • promisify
  • suppress

Utility functions

delay

type DelayType = (ms: number) => Promise<void>;

/**
 * Creates a promise that is scheduled to resolve after a set delay.
 */
const delay: DelayType;

map

For the record, this function is just a thin-wrapper around Bluebird#map.

This method is identical to Bluebird#map except that the concurrency setting can be overridden using BLUEFEATHER_MAX_CONCURRENCY environment variable. Controlling max concurrency using environment variables enables debugging of the codebase without refactoring the code.

type MapperType<T, R> = (currentValue: T, index: number, values: $ReadOnlyArray<T>) => R;

type MapConfigurationType = {|
  +concurrency: number
|};

type MapType<T, R> = (values: $ReadOnlyArray<T>, mapper: MapperType<T, R>, configuration?: MapConfigurationType) => Promise<$ReadOnlyArray<R>>;

const map: MapType<*, *>;

mapSeries

type CallbackType<T, R> = (currentValue: T, index: number, values: $ReadOnlyArray<T>) => R;

type MapSeriesType<T, R> = (values: $ReadOnlyArray<T>, mapper: CallbackType<T, R>) => Promise<$ReadOnlyArray<R>>;

/**
 * Creates a promise that is scheduled to resolve after a set delay.
 */
const mapSeries: MapSeriesType<*, *>;

promisify

/**
 * @property multipleArguments Makes the resulting promise fulfill with an array of the callback's success value(s).
 */
type PromisifyOptionsType = {|
  multipleArguments?: boolean
|};

type PromisifyType = (nodeFunction: Function, options?: PromisifyOptionsType) => Function;

/**
 * Creates a function that when executed returns a promise whose fait depends
 * on the callback provided as the last parameter to the wrapped function.
 */
const promisify: PromisifyType;

suppress

type SuppressType = <T: Promise<*>>(
  ErrorConstructor: Class<Error> | (error: Error) => boolean,
  promise: T
) => T | Promise<void>;

/**
 * Suppresses errors that are instance of ErrorConstructor.
 */
const suppress: SuppressType;