someLimit.mjs

import findIndexLimit from './findIndexLimit.mjs'

/**
 * Returns `true` if at least one element of an iterable pass a truth test and `false` otherwise.
 *
 * The calls to `iteratee` will run in parallel, up to a concurrency limit. If any truth test returns `true`
 * the promise is immediately resolved.
 *
 * Whenever a test returns `true`, all the remaining tasks will be cancelled as long
 * as they didn't started already. In case of exception in one of the `iteratee` calls the promise
 * returned by this function will be rejected with the exception and the remaining pending
 * tasks will also be cancelled. In the very specific case where a test returns `true` and an
 * already started task throws an exception that exception will be plainly ignored.
 *
 * @param {Iterable} iterable An iterable object.
 * @param {Function} iteratee A function that will be called with each member of the iterable. It will receive
 * three arguments:
 *   * `value`: The current value to process
 *   * `index`: The index in the iterable. Will start from 0.
 *   * `iterable`: The iterable on which the operation is being performed.
 * @param {number} concurrency The number of times `iteratee` can be called concurrently.
 * @returns {Promise} A promise that will be resolved to `true` if at least one value pass the truth test and `false`
 * if none of them do. That promise will be rejected if one of the truth test throws an exception.
 * @example
 * import { someLimit, asyncRoot, sleep } from 'modern-async'
 *
 * asyncRoot(async () => {
 *   const array = [1, 2, 3]
 *
 *   const result = await someLimit(array, async (v) => {
 *     // these calls will be performed in parallel with a maximum of 2
 *     // concurrent calls
 *     await sleep(10) // waits 10ms
 *     return v % 2 === 0
 *   }, 2)
 *   console.log(result) // prints true
 *   // total processing time should be ~ 10ms
 * })
 */
async function someLimit (iterable, iteratee, concurrency) {
  const index = await findIndexLimit(iterable, iteratee, concurrency)
  const result = index !== -1
  return result
}

export default someLimit