get-closest/index.js

Compare your item to items in an array and get the closest one.

/**
* @license get-closest https://github.com/cosmosio/get-closest
*
* The MIT License (MIT)
*
* Copyright (c) 2014-2017 Olivier Scherrer <pode.fr@gmail.com>
*/
"use strict";

/**
 * Get the closest number in an array
 * @param {Number} item the base number
 * @param {Array} array the array to search into
 * @param {Function} getDiff returns the difference between the base number and
 *   and the currently read item in the array. The item which returned the smallest difference wins.
 * @private
 */
function _getClosest(item, array, getDiff) {
    var closest,
        diff;

    if (!Array.isArray(array)) {
        throw new Error("Get closest expects an array as second argument");
    }

    array.forEach(function (comparedItem, comparedItemIndex) {
        var thisDiff = getDiff(comparedItem, item);

        if (thisDiff >= 0 && (typeof diff == "undefined" || thisDiff < diff)) {
            diff = thisDiff;
            closest = comparedItemIndex;
        }
    });

    return closest;
}

module.exports = {

  /**
   * Get the closest number in an array given a base number
   * Example: closest(30, [20, 0, 50, 29]) will return 3 as 29 is the closest item
   * @param {Number} item the base number
   * @param {Array} array the array of numbers to search into
   * @returns {Number} the index of the closest item in the array
   */
  number: function closestNumber(item, array) {
      return _getClosest(item, array, function (comparedItem, item) {
          return Math.abs(comparedItem - item);
      });
  },

  /**
   * Get the closest greater number in an array given a base number
   * Example: closest(30, [20, 0, 50, 29]) will return 2 as 50 is the closest greater item
   * @param {Number} item the base number
   * @param {Array} array the array of numbers to search into
   * @returns {Number} the index of the closest item in the array
   */
  greaterNumber: function closestGreaterNumber(item, array) {
      return _getClosest(item, array, function (comparedItem, item) {
          return comparedItem - item;
      });
  },

  /**
   * Get the closest lower number in an array given a base number
   * Example: closest(30, [20, 0, 50, 29]) will return 0 as 20 is the closest lower item
   * @param {Number} item the base number
   * @param {Array} array the array of numbers to search into
   * @returns {Number} the index of the closest item in the array
   */
  lowerNumber: function closestLowerNumber(item, array) {
    return _getClosest(item, array, function (comparedItem, item) {
        return item - comparedItem;
    });
  },

  /**
   * Get the closest item in an array given a base item and a comparator function
   * Example (closest("lundi", ["mundi", "mardi"], getLevenshteinDistance)) will return 0 for "lundi"
   * @param {*} item the base item
   * @param {Array} array an array of items
   * @param {Function} comparator a comparatof function to compare the items
   *
   * The function looks like:
   *
   * // comparedItem comes from the array
   * // baseItem is the item to compare the others to
   * // It returns a number
   * function comparator(comparedItem, baseItem) {
   *     return comparedItem - baseItem;
   * }
   */
  custom: function closestCustom(item, array, comparator) {
    return _getClosest(item, array, comparator);
  }

};