redux-saga/es/internal/sagaHelpers/takeLatest.js

Saga middleware for Redux to handle Side Effects

import fsmIterator, { qEnd, safeName } from './fsmIterator';
import { cancel, take, fork } from '../io';
import { END } from '../channel';

export default function takeLatest(patternOrChannel, worker) {
  for (var _len = arguments.length, args = Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
    args[_key - 2] = arguments[_key];
  }

  var yTake = { done: false, value: take(patternOrChannel) };
  var yFork = function yFork(ac) {
    return { done: false, value: fork.apply(undefined, [worker].concat(args, [ac])) };
  };
  var yCancel = function yCancel(task) {
    return { done: false, value: cancel(task) };
  };

  var task = void 0,
      action = void 0;
  var setTask = function setTask(t) {
    return task = t;
  };
  var setAction = function setAction(ac) {
    return action = ac;
  };

  return fsmIterator({
    q1: function q1() {
      return ['q2', yTake, setAction];
    },
    q2: function q2() {
      return action === END ? [qEnd] : task ? ['q3', yCancel(task)] : ['q1', yFork(action), setTask];
    },
    q3: function q3() {
      return ['q1', yFork(action), setTask];
    }
  }, 'q1', 'takeLatest(' + safeName(patternOrChannel) + ', ' + worker.name + ')');
}