fluorine-lib/es/distinctSelector.js

Reactive state and side effect management for React using a single stream of actions

import { Observable } from 'rxjs/Observable';
import assert from './util/assert';

export default function distinctSelector(keys) {
  var _this = this;

  var _containsStrings = keys.reduce(function (acc, str) {
    return acc && typeof str === 'string';
  }, true);
  assert(Array.isArray(keys), 'Expected `keys` to be an array.');
  assert(_containsStrings, 'Expected `keys` to contain only keys.');

  return Observable.create(function (observer) {
    var last = undefined;
    return _this.subscribe(function (value) {
      if (value === undefined || value === null || last === value) {
        return;
      }

      var changed = false;
      var result = {};

      for (var _iterator = keys, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
        var _ref;

        if (_isArray) {
          if (_i >= _iterator.length) break;
          _ref = _iterator[_i++];
        } else {
          _i = _iterator.next();
          if (_i.done) break;
          _ref = _i.value;
        }

        var key = _ref;

        result[key] = value[key];
        if (!changed || !last || result[key] !== last[key]) {
          changed = true;
        }
      }

      if (changed) {
        observer.next(result);
      }

      last = value;
    }, function (err) {
      return observer.error(err);
    }, function () {
      return observer.complete();
    });
  });
}