Redux Saga helpers

helpers.js

import { call, cancel, fork, take } from 'redux-saga/effects';

export function takeLatestPerKey(patternOrChannel, worker, keySelector, ...args) {
  return fork(function*() {
    const tasks = {};

    while (true) {
      const action = yield take(patternOrChannel);
      const key = yield call(keySelector, action);

      if (tasks[key]) {
        yield cancel(tasks[key]);
      }

      tasks[key] = yield fork(worker, ...args, action);
    }
  });
}

export function takeLeadingPerKey(patternOrChannel, worker, keySelector, ...args) {
  return fork(function*() {
    const tasks = {};

    while (true) {
      const action = yield take(patternOrChannel);
      const key = yield call(keySelector, action);

      if (!(tasks[key] && tasks[key].isRunning())) {
        tasks[key] = yield fork(worker, ...args, action);
      }
    }
  });
}