join-by-keys

Join an array of objects on a common key or keys.

Example

var join = require('join-by-keys')

var result
  , data

data = [
    {
      'i': 0
      'j': 0
      'v': 1
    }
  , {
      'i': 0
      'j': 0
      'v': 2
    }
  , {
      'i': 1
      'j': 0
      'v': 3
    }
  , {
      'i': 1
      'j': 1
      'v': 4
    }
  , {
      'i': 1
      'j': 1
      'v': 5
    }
]

join(data, ['i', 'j']) 
// returns:
// [
//     {i: 0, j: 0, v: [1, 2]}
//   , {i: 1, j: 0, v: [3]}
//   , {i: 1, j: 1, v: [4, 5]}
// ]

API

The module exports a function:

function(data, keys) -> joinedData

Arguments

• data is assumed to be an array of JavaScript objects to join.
• keys is an array of strings representing the names of attributes whose values should be used to join the data

Return value

joinedData is an array of JavaScript objects: The join of the data on the specified keys. It is computed as follows:

• Find all the elements of data with the same value in each of the keys slots.
• Create a new object representing the join of the matching elements by doing the iterating over each key and applying the following rules:
  • If key is in keys, on the new object, set the key to the value of the first matching object. (It doesn't matter which you choose, since they are all the same anyway).
  • If key is not in keys, in the returned object, set key to an array holding all the values for the given key found on all of the matching objects.

License

This project is licensed under the Apache License, Version 2.0. See LICENSE for the full license.