pnpm/lib/node_modules/most/src/combinator/observe.js

Fast, disk space efficient package manager

/** @license MIT License (c) copyright 2010-2016 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

import { withDefaultScheduler as run } from '../runSource'
import { tap } from './transform'

/**
 * Observe all the event values in the stream in time order. The
 * provided function `f` will be called for each event value
 * @param {function(x:T):*} f function to call with each event value
 * @param {Stream<T>} stream stream to observe
 * @return {Promise} promise that fulfills after the stream ends without
 *  an error, or rejects if the stream ends with an error.
 */
export function observe (f, stream) {
  return drain(tap(f, stream))
}

/**
 * "Run" a stream by creating demand and consuming all events
 * @param {Stream<T>} stream stream to drain
 * @return {Promise} promise that fulfills after the stream ends without
 *  an error, or rejects if the stream ends with an error.
 */
export function drain (stream) {
  return run(stream.source)
}