reduce-by

Turn an array of values into an object by using a function to determine the key an item belongs to and a function to determine how an item is grouped under that key. reduceBy is like groupBy, but more generic.

install

$ npm install reduce-by

example

const reduceBy = require('reduce-by')

// group items by concatenating and use first character as the key
reduceBy(
  (group, v) => group + v,
  () => '',
  v => v.slice(0, 1),
  [ 'foo', 'bar', 'baz' ]
)
// => { f: 'foo', b: 'barbaz' }

api

reduceBy(groupReducer, getInitialGroupValue, getKey, array)

• groupReducer(group, value) function that takes the accumulated group value and a value to be grouped and returns the new accumulated group value
  • group accumulated group value
  • value value to be added to the group
  • => group accumulated group value
• getInitialGroupValue() function that returns the initial value for groups
  • => initialGroupValue
• getKey(value) function that takes value and returns the key that value belongs to
  • => key the key the value should be grouped under
• array: [] an array of items to be turned into an object
• => object