leftJoin

• leftJoin

Input two arrays left and right, and return the array formed by performing a left join of left with right. This is commonly used to combine arrays of objects that contain related information, similar to how it is done in SQL.

Additionally, it accepts two parameters: leftKey and rightKey. These can be field paths of getByPath or callback functions, used to provide identifiers to distinguish elements. The merge function is used to generate the return array objects.

Added in v0.0.1

Usage

import { leftJoin } from 'parsnip-kit'

const leftArray0 = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' },
]
const rightArray0 = [
  { id: 1, age: 25 },
  { id: 3, age: 30 },
]

leftJoin(
  leftArray0,
  rightArray0,
  (item) => item.id,
  (item) => item.id,
  (left, right) => ({ ...left, ...(right || {}) }),
) // [{ id: 1, name: 'Alice', age: 25 }, { id: 2, name: 'Bob' }, { id: 3, name: 'Charlie', age: 30 }]


const leftArray1 = [
  { id: 1, info: { name: 'Alice', age: 25 } },
  { id: 2, info: { name: 'Bob', age: 35 } },
  { id: 3, info: { name: 'Charlie', age: 30 } },
]
const rightArray1 = [
  { name: 'Alice', experience: ['software engineer', 'designer'] },
  { name: 'Charlie', experience: ['freelance'] },
]

leftJoin(
  leftArray1,
  rightArray1,
  'info.name',
  'name',
  (left, right) => ({ name: left.info.name, job: right?.experience[0] ?? null }),
) // [{ name: 'Alice', job: 'software engineer' }, { name: 'Bob', job: null }, { name: 'Charlie', job: 'freelance' }]

API

Type Parameter

Arg	Type	Description
T	extends object	Type of elements of left array in a left join
U	extends object	Type of elements of right array in a left join
R	extends object	Type of elements of array returned

Arguments

Arg	Type	Optional	Default	Description
left	T[]	false	undefined	The left array in a left join
right	U[]	false	undefined	The right array in a left join
leftKey	string | ((item: T, index: number, arr: T[]) => any)	false	undefined	Provide an identifier to distinguish elements in the left array
rightKey	string | ((item: U, index: number, arr: U[]) => any)	false	undefined	Provide an identifier to distinguish elements in the right array
merge	(left: T, right: U | undefined) => R	false	undefined	Return the result of merging elements from left and right arrays.

Returns

Type
R[]