1 | ;
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2 |
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3 | Object.defineProperty(exports, "__esModule", {
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4 | value: true
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5 | });
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6 | exports.default = reduce;
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7 |
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8 | var _eachOfSeries = require('./eachOfSeries');
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9 |
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10 | var _eachOfSeries2 = _interopRequireDefault(_eachOfSeries);
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11 |
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12 | var _noop = require('lodash/noop');
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13 |
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14 | var _noop2 = _interopRequireDefault(_noop);
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15 |
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16 | var _once = require('./internal/once');
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17 |
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18 | var _once2 = _interopRequireDefault(_once);
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19 |
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20 | var _wrapAsync = require('./internal/wrapAsync');
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21 |
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22 | var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
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23 |
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24 | function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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25 |
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26 | /**
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27 | * Reduces `coll` into a single value using an async `iteratee` to return each
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28 | * successive step. `memo` is the initial state of the reduction. This function
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29 | * only operates in series.
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30 | *
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31 | * For performance reasons, it may make sense to split a call to this function
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32 | * into a parallel map, and then use the normal `Array.prototype.reduce` on the
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33 | * results. This function is for situations where each step in the reduction
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34 | * needs to be async; if you can get the data before reducing it, then it's
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35 | * probably a good idea to do so.
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36 | *
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37 | * @name reduce
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38 | * @static
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39 | * @memberOf module:Collections
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40 | * @method
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41 | * @alias inject
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42 | * @alias foldl
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43 | * @category Collection
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44 | * @param {Array|Iterable|Object} coll - A collection to iterate over.
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45 | * @param {*} memo - The initial state of the reduction.
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46 | * @param {AsyncFunction} iteratee - A function applied to each item in the
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47 | * array to produce the next step in the reduction.
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48 | * The `iteratee` should complete with the next state of the reduction.
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49 | * If the iteratee complete with an error, the reduction is stopped and the
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50 | * main `callback` is immediately called with the error.
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51 | * Invoked with (memo, item, callback).
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52 | * @param {Function} [callback] - A callback which is called after all the
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53 | * `iteratee` functions have finished. Result is the reduced value. Invoked with
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54 | * (err, result).
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55 | * @example
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56 | *
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57 | * async.reduce([1,2,3], 0, function(memo, item, callback) {
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58 | * // pointless async:
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59 | * process.nextTick(function() {
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60 | * callback(null, memo + item)
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61 | * });
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62 | * }, function(err, result) {
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63 | * // result is now equal to the last value of memo, which is 6
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64 | * });
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65 | */
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66 | function reduce(coll, memo, iteratee, callback) {
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67 | callback = (0, _once2.default)(callback || _noop2.default);
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68 | var _iteratee = (0, _wrapAsync2.default)(iteratee);
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69 | (0, _eachOfSeries2.default)(coll, function (x, i, callback) {
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70 | _iteratee(memo, x, function (err, v) {
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71 | memo = v;
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72 | callback(err);
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73 | });
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74 | }, function (err) {
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75 | callback(err, memo);
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76 | });
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77 | }
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78 | module.exports = exports['default']; |
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