concat.js

  1. 'use strict';
  3. const { Each } = require('./each');
  4. const { concatArray } = require('./internal/util');
  5. const { setParallel } = require('./internal/collection');
  7. class Concat extends Each {
  8.   constructor(collection, iterator) {
  9.     super(collection, iterator, set);
  10.   }
  12.   _callResolve(value, index) {
  13.     this._result[index] = value;
  14.     if (--this._rest === 0) {
  15.       this._promise._resolve(concatArray(this._result));
  16.     }
  17.   }
  18. }
  20. module.exports = { concat, Concat };
  22. function set(collection) {
  23.   setParallel.call(this, collection);
  24.   this._result = Array(this._rest);
  25.   return this;
  26. }
  28. /**
  29.  * `Aigle.concat` has almost the same functionality as `Array#concat`.
  30.  * It iterates all elements of `collection` and executes `iterator` using each element on parallel.
  31.  * The `iterator` needs to return a promise or something.
  32.  * If a promise is returned, the function will wait until the promise is fulfilled.
  33.  * Then the result will be assigned to an array, the role is the same as `Array#concat`.
  34.  * All of them are finished, the function will return an array as a result.
  35.  * @param {Array|Object} collection
  36.  * @param {Function} iterator
  37.  * @return {Aigle} Returns an Aigle instance
  38.  * @example
  39.  * const order = [];
  40.  * const collection = [1, 4, 2];
  41.  * const iterator = (num, index, collection) => {
  42.  *   return Aigle.delay(num * 10)
  43.  *     .then(() => {
  44.  *       order.push(num);
  45.  *       return num;
  46.  *     });
  47.  * };
  48.  * Aigle.concat(collection, iterator)
  49.  *   .then(array => {
  50.  *     console.log(array); // [1, 2, 4];
  51.  *     console.log(order); // [1, 2, 4];
  52.  *   });
  53.  *
  54.  * @example
  55.  * const order = [];
  56.  * const collection = { a: 1, b: 4, c: 2 };
  57.  * const iterator = (num, key, collection) => {
  58.  *   return Aigle.delay(num * 10)
  59.  *     .then(() => {
  60.  *       order.push(num);
  61.  *       return num;
  62.  *     });
  63.  * };
  64.  * Aigle.concat(collection, iterator)
  65.  *   .then(array => {
  66.  *     console.log(array); // [1, 2, 4];
  67.  *     console.log(order); // [1, 2, 4];
  68.  *   });
  69.  */
  70. function concat(collection, iterator) {
  71.   return new Concat(collection, iterator)._execute();
  72. }