JAVASCRIPT   9

transform.js

Guest on 21st May 2021 06:51:43 AM

  1. 'use strict';
  2.  
  3. Object.defineProperty(exports, "__esModule", {
  4.     value: true
  5. });
  6. exports.default = transform;
  7.  
  8. var _isArray = require('lodash/isArray');
  9.  
  10. var _isArray2 = _interopRequireDefault(_isArray);
  11.  
  12. var _noop = require('lodash/noop');
  13.  
  14. var _noop2 = _interopRequireDefault(_noop);
  15.  
  16. var _eachOf = require('./eachOf');
  17.  
  18. var _eachOf2 = _interopRequireDefault(_eachOf);
  19.  
  20. var _once = require('./internal/once');
  21.  
  22. var _once2 = _interopRequireDefault(_once);
  23.  
  24. var _wrapAsync = require('./internal/wrapAsync');
  25.  
  26. var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
  27.  
  28. function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
  29.  
  30. /**
  31.  * A relative of `reduce`.  Takes an Object or Array, and iterates over each
  32.  * element in series, each step potentially mutating an `accumulator` value.
  33.  * The type of the accumulator defaults to the type of collection passed in.
  34.  *
  35.  * @name transform
  36.  * @static
  37.  * @memberOf module:Collections
  38.  * @method
  39.  * @category Collection
  40.  * @param {Array|Iterable|Object} coll - A collection to iterate over.
  41.  * @param {*} [accumulator] - The initial state of the transform.  If omitted,
  42.  * it will default to an empty Object or Array, depending on the type of `coll`
  43.  * @param {AsyncFunction} iteratee - A function applied to each item in the
  44.  * collection that potentially modifies the accumulator.
  45.  * Invoked with (accumulator, item, key, callback).
  46.  * @param {Function} [callback] - A callback which is called after all the
  47.  * `iteratee` functions have finished. Result is the transformed accumulator.
  48.  * Invoked with (err, result).
  49.  * @example
  50.  *
  51.  * async.transform([1,2,3], function(acc, item, index, callback) {
  52.  *     // pointless async:
  53.  *     process.nextTick(function() {
  54.  *         acc.push(item * 2)
  55.  *         callback(null)
  56.  *     });
  57.  * }, function(err, result) {
  58.  *     // result is now equal to [2, 4, 6]
  59.  * });
  60.  *
  61.  * @example
  62.  *
  63.  * async.transform({a: 1, b: 2, c: 3}, function (obj, val, key, callback) {
  64.  *     setImmediate(function () {
  65.  *         obj[key] = val * 2;
  66.  *         callback();
  67.  *     })
  68.  * }, function (err, result) {
  69.  *     // result is equal to {a: 2, b: 4, c: 6}
  70.  * })
  71.  */
  72. function transform(coll, accumulator, iteratee, callback) {
  73.     if (arguments.length <= 3) {
  74.         callback = iteratee;
  75.         iteratee = accumulator;
  76.         accumulator = (0, _isArray2.default)(coll) ? [] : {};
  77.     }
  78.     callback = (0, _once2.default)(callback || _noop2.default);
  79.     var _iteratee = (0, _wrapAsync2.default)(iteratee);
  80.  
  81.     (0, _eachOf2.default)(coll, function (v, k, cb) {
  82.         _iteratee(accumulator, v, k, cb);
  83.     }, function (err) {
  84.         callback(err, accumulator);
  85.     });
  86. }
  87. module.exports = exports['default'];

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