data-fns/src/lib/mapAt.test.ts

This library provides utility functions for working with array data that are useful in many contexts, including creative coding. It offers generic functions that perform common operations such as offsetting an array, generating an array based on a callbac

import { mapAt } from './mapAt'

describe('mapAt', () => {
  test('should return a new array with the modified item', () => {
    const myArray = [1, 2, 3, 4, 5]
    const index = 2
    const mapFn = (item: number) => item * 2
    const modifiedArray = mapAt(myArray, index, mapFn)
    expect(modifiedArray).toEqual([1, 2, 6, 4, 5])
  })

  test('should not modify the original array', () => {
    const myArray = [1, 2, 3, 4, 5]
    const index = 2
    const mapFn = (item: number) => item * 2
    const modifiedArray = mapAt(myArray, index, mapFn)
    expect(myArray).toEqual([1, 2, 3, 4, 5])
    expect(modifiedArray).not.toBe(myArray)
  })

  test('should throw an error if the index is out of range', () => {
    const myArray = [1, 2, 3, 4, 5]
    const index = 10
    const mapFn = (item: number) => item * 2
    expect(() => mapAt(myArray, index, mapFn)).toThrowError(
      'Index out of range'
    )
  })
    
  test('should return the original array if mapFn returns the same value', () => {
    const myArray = [1, 2, 3, 4, 5]
    const index = 2
    const mapFn = (item: number) => item
    const modifiedArray = mapAt(myArray, index, mapFn)
    expect(modifiedArray).toBe(myArray)
  })

    
})