magical comprehensions for JS Object instances

objectUtils.js

/**
 * @title objectUtils.js
 * @description magical comprehensions for JS Object instances
 * @author Max L Dolgov, plugn@github.com
 *
 * Here is `var` keyword for ability to re-declare functions, 
 * it makes tweaking functions in browser console possible.
 * 
 */

var mapCollectionByProp = (list, fieldName) => list.reduce( (acc, v) => ({ ...acc, [v[fieldName]]: v }), {})

var composeObject = (object, iterator = val => val, keys = Object.keys(object)) =>
  keys.reduce((acc, field) => ({ ...acc, ...iterator(object[field], field)}), {})

var filterObject = (object, callback) => composeObject(object, (val, key) => (callback(val, key) ? {[key]: val} : {}))
var mapObject = (object, callback) => composeObject(object, (val, key) => ({[key]: callback(val, key)}))

/** 
 * changes Object items recursively
 * callback gets object's value and key pair and may return object with multiple keys
 *
 * @param source {object|array|*} - 
 * @param mapper {function} -> {object}
 * @returns {object|array|*}
 */
function walkObject (source, mapper = (v, k) => ({[k]: v})) {
  if (typeof source !== 'object' || source === null || source === undefined) {
    return source
  }

  if (Array.isArray(source)) {
    return source.map(v => walkObject(v, mapper))
  }

  return Object.keys(source).reduce((acc, key) => ({
      ...acc,
      ...(mapper(walkObject(source[key], mapper), key))
    }),
  {})
}

var getCycleIndex = (position, length) => (position + length) % length
function moveListItem(list, index, step) {
  const position = getCycleIndex(index + step, list.length)
  list.splice(position, 0, list.splice(index, 1)[0])
}

var range = (min, max) => Array.from(Array(max - min + 1).keys()).map(v => v + min)
var uniqList = list => list.filter((v, i) => list.indexOf(v) === i)
var initList = (length, initialValue) => Array(length).fill(null).map(item => initialValue)


var getFlattenTreeReducer = (subTreePropName = 'children') => {
  const reducer = (acc, item, index) =>
    ([
      ...acc,
      {...item, _treeNodeId: String(index)},
      ...(item[subTreePropName]
        ? item[subTreePropName].reduce(reducer, [])
          .map(v => ({...v, _treeNodeId: String(`${index}:${v._treeNodeId}`) }))
        : [])
    ])
  return reducer
}
var flattenTree = (treeData = [], subTreePropName) => treeData.reduce(getFlattenTreeReducer(subTreePropName), [])

/**
 * gets value of nested property
 *
 * @param obj {object|array}
 * @param path {string}
 * @param def - default value
 * @returns {*}
 */
export function getNested(obj, path, def = undefined){
  const splitter = '[].'
  const listQueryParts = String(path).split(splitter)
  if (listQueryParts && listQueryParts.length > 1) {
    const list = getNested(obj, listQueryParts[0])
    if (Array.isArray(list)) {
      return list.map(val => getNested(val, listQueryParts.slice(1).join(splitter)))
    }
  }

  let key, val = obj
  let arr = String(path)
    .replace(/'|"|\]/g,'')
    .replace(/\[/g,'.')
    .split('.')
  while ((key = arr.shift()) && 'object' === typeof val && val) {
    val = undefined === val[key] ? def : val[key]
  }
  return val
}

// EOF %)