a multi-pluck mixin for lodash

multiPluck.coffee

ld = require 'lodash'
assert = require("assert")

multiPluck = (input,keys) ->

  pluckFrom = (o,keys) ->
    result = {}
    for k in keys
      unless result[k]?
        result[k] = o[k] or undefined
    result

  r = null
  if Array.isArray(input)
    r = []
    for item in input
      r.push( pluckFrom(item, keys))
  else
    r = pluckFrom(input, keys)

  r

ld.mixin(multiPluck: multiPluck)

arr = [{a: 4, b:7, c:19}
    {a: 6, c:4, b:12}
      {a: 4, c:3, b:5}]

r0 = ld.multiPluck(arr, ['a','c'])
r1 = ld.multiPluck(arr[1], ['c', 'b'])

console.dir(r0) # [ { a: 4, c: 19 }, { a: 6, c: 4 }, { a: 4, c: 3 } ]
console.dir(r1) # { c: 4, b: 12 }

assert(r0[0].a == 4)
assert(r0[0].c == 19)
assert(r0[0].b == undefined)

assert(r1.a == undefined)
assert(r1.b == 12)
assert(r1.c == 4)

filtered = ld(arr).where(a:4).multiPluck(['c','b'])
console.dir(filtered.value()) # [ { c: 19, b: 7 }, { c: 3, b: 5 } ]