batch mixin for underscore

.gitignore

node_modules

batch_mixin.coffee

batch = (collection, size) ->

  return unless collection.slice?
  numberofbatches = Math.ceil (collection.length / size)

  for batchindex in [0...numberofbatches]
    do (batchindex) ->
      start = batchindex * size
      end = start + size
      collection[start...end]

exports = module.exports = (_) ->
  _.mixin {
    batch: batch }

batch_mixin_spec.coffee

_ = require 'underscore'
require('../batch_mixin')(_)

describe 'batching', ->
  it 'wont work on noncollection', ->
    batches = _.batch 2, 10

    expect(batches).toBeUndefined

  it 'empty', ->
    batches = _.batch [], 10

    expect(batches).toEqual []

  it 'same size', ->
    batches = _.batch [1..5], 5

    expect(batches.length).toBe 1

  it 'real thing', ->
    batches = _.chain([1..6]).batch(5).value()
    expect(batches.length).toBe 2
    expect(batches[0]).toEqual [1..5]
    expect(batches[1]).toEqual [6]

    batches = _.batch [1..3], 5
    expect(batches.length).toBe 1
    expect(batches[0]).toEqual [1..3]

    batches = _.batch [1..10], 3
    expect(batches.length).toBe 4

    batches = _.batch [1..10], 100
    expect(batches.length).toBe 1

package.json

{
  "name": "batch",
  "version": "0.0.0",
  "description": "batch mixin for underscore",
  "main": "index.js",
  "scripts": {
    "test": "jasmine-node --autotest --color --coffee ."
  },
  "repository": {
    "type": "git",
    "url": "https://gist.github.com/4576815.git"
  },
  "author": "Ryan Cromwell Sr",
  "license": "BSD",
  "dependencies": {
    "jasmine-node": "~1.0.28",
    "underscore": "~1.4.3"
  }
}