merge-by-key

Object merge utility

This repository contains two utility functions, mergeBy and linearMerge, for merging objects in an array based on a specified key or deep key. These functions can be particularly useful for consolidating data from various sources or handling data transformation in applications.

Functions

mergeBy

Merges objects in an array based on a specified key or deep key. If two objects have the same key value, their properties are combined.

Signature

function mergeBy<T extends object>(array: T[], key: keyof T): T[]

Parameters

array: An array of objects to be merged.

key: The key used to determine if two objects should be merged.

Returns

An array of merged objects.

Example

const data = [
    { id: 1, name: 'Alice', age: 30 },
    { id: 2, name: 'Bob', age: 25 },
    { id: 1, name: 'Alice', age: 31 }, // Duplicate ID with a different age
    { id: 3, name: 'Charlie', age: 35 },
];

const merged = mergeBy(data, 'id');
console.log(merged);
// { id: 1, name: 'Alice', age: 31 }, // Merged
// { id: 2, name: 'Bob', age: 25 },
// { id: 3, name: 'Charlie', age: 35 },

linearMerge

Linear merges objects in an array based on a specified key or deep key. Compares only with the next item if exists. If two objects have the same key value, their properties are combined using Object.assign or with mergeFn.

function linearMerge<T extends object>(array: T[] = [], key: keyof T, mergeFn: (next: T, current: T) => T = Object.assign): T[]

Parameters

array: An array of objects to be merged.

key: The key used to determine if two objects should be merged.

mergeFn: An optional function to define how the merging should be performed. Defaults to Object.assign.

Returns

An array of merged objects.

Example

import {linearMerge} from "./index";

const data = [
    {id: 1, name: 'Alice'},
    {id: 1, name: 'Alice Smith'},
    {id: 2, name: 'Bob'},
    {id: 2, name: 'Bob Brown'},
    {id: 3, name: 'Charlie'}
];

const merged = linearMerge(data, 'id');
console.log(merged);
// { id: 1, name: 'Alice' },
// { id: 2, name: 'Bob' },
// { id: 3, name: 'Charlie' }

const data: Person[] = [
    { id: 1, name: 'Alice', age: 25 },
    { id: 1, name: 'Alice Smith', age: 30 }
];

const customMerge = (next: Person, current: Person) => ({
    id: current.id,
    name: current.name + ' & ' + next.name,
    age: Math.max(current.age, next.age)
});

const merged = linearMerge<Person>(data, 'id', customMerge);
console.log(merged);
// { id: 1, name: 'Alice & Alice Smith', age: 30 }

Installation

You can install this package via npm:

npm install merge-by-key

Testing

You can set up tests using Jest to ensure that the functions work as expected. Here’s an example of how to write tests for these functions:

npx test