85 lines
2.7 KiB
JavaScript
85 lines
2.7 KiB
JavaScript
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'use strict';
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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exports.default = transform;
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var _isArray = require('lodash/isArray');
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var _isArray2 = _interopRequireDefault(_isArray);
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var _noop = require('lodash/noop');
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var _noop2 = _interopRequireDefault(_noop);
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var _eachOf = require('./eachOf');
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var _eachOf2 = _interopRequireDefault(_eachOf);
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var _once = require('./internal/once');
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var _once2 = _interopRequireDefault(_once);
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function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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/**
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* A relative of `reduce`. Takes an Object or Array, and iterates over each
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* element in series, each step potentially mutating an `accumulator` value.
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* The type of the accumulator defaults to the type of collection passed in.
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*
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* @name transform
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* @static
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* @memberOf module:Collections
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* @method
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* @category Collection
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* @param {Array|Iterable|Object} coll - A collection to iterate over.
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* @param {*} [accumulator] - The initial state of the transform. If omitted,
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* it will default to an empty Object or Array, depending on the type of `coll`
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* @param {Function} iteratee - A function applied to each item in the
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* collection that potentially modifies the accumulator. The `iteratee` is
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* passed a `callback(err)` which accepts an optional error as its first
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* argument. If an error is passed to the callback, the transform is stopped
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* and the main `callback` is immediately called with the error.
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* Invoked with (accumulator, item, key, callback).
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* @param {Function} [callback] - A callback which is called after all the
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* `iteratee` functions have finished. Result is the transformed accumulator.
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* Invoked with (err, result).
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* @example
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*
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* async.transform([1,2,3], function(acc, item, index, callback) {
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* // pointless async:
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* process.nextTick(function() {
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* acc.push(item * 2)
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* callback(null)
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* });
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* }, function(err, result) {
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* // result is now equal to [2, 4, 6]
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* });
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*
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* @example
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*
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* async.transform({a: 1, b: 2, c: 3}, function (obj, val, key, callback) {
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* setImmediate(function () {
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* obj[key] = val * 2;
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* callback();
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* })
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* }, function (err, result) {
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* // result is equal to {a: 2, b: 4, c: 6}
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* })
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*/
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function transform(coll, accumulator, iteratee, callback) {
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if (arguments.length === 3) {
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callback = iteratee;
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iteratee = accumulator;
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accumulator = (0, _isArray2.default)(coll) ? [] : {};
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}
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callback = (0, _once2.default)(callback || _noop2.default);
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(0, _eachOf2.default)(coll, function (v, k, cb) {
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iteratee(accumulator, v, k, cb);
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}, function (err) {
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callback(err, accumulator);
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});
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}
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module.exports = exports['default'];
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