data-fns/src/lib/mapAt.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

/**
 * Maps an item in an array at a specified index to a new value.
 * @param array The array to map the item in.
 * @param index The index of the item to map.
 * @param mapFn A function that maps the item to a new value.
 * @returns A new array with the mapped item.
 * @example
 * const originalArray = [1, 2, 3, 4, 5]
 * const mappedArray = mapAt(originalArray, 2, (item) => item * 2)
 * // Returns [1, 2, 6, 4, 5]
 */
export const mapAt = <T>(array: Array<T>, index: number, mapFn: (item: T) => T): Array<T> => {
  // Check that the index is within the bounds of the array
  if (index > array.length || index < 0) {
    throw new Error('Index out of range')
  }

  // Get the item at the specified index
  const item = array[index]

  // Map the item to a new value using the mapFn function
  const newItem = mapFn(item)

  // If the new value is the same as the original value, return the original array
  if (newItem === item) {
    return array
  }

  // Create a new array with the mapped item
  const newArray = array.slice()
  newArray[index] = mapFn(array[index])

  return newArray
}