data-fns/src/lib/cyclic.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 { cyclic } from './cyclic'
import { getItem } from './getItem'

describe('cyclic', () => {
  it('returns the first element when index is 0', () => {
    const myArray = [1, 2, 3]
    expect(getItem(0, myArray, cyclic)).toEqual(1)
  })

  it('returns the first element when index is equal to array length', () => {
    const myArray = [1, 2, 3]
    expect(getItem(3, myArray, cyclic)).toEqual(1)
  })

  it('returns the second element when index is equal to 1', () => {
    const myArray = [1, 2, 3]
    expect(getItem(1, myArray, cyclic)).toEqual(2)
  })

  it('returns the second element when index is greater than array length', () => {
    const myArray = [1, 2, 3]
    expect(getItem(4, myArray, cyclic)).toEqual(2)
  })

  it('returns the first element when index is a multiple of array length', () => {
    const myArray = [1, 2, 3]
    expect(getItem(6, myArray, cyclic)).toEqual(1)
  })

  it('returns the correct element when array has only one element', () => {
    const myArray = [1]
    expect(getItem(0, myArray, cyclic)).toEqual(1)
    expect(getItem(1, myArray, cyclic)).toEqual(1)
  })

  it('returns the correct element when array is empty', () => {
    const myArray: Array<number> = []
    expect(getItem(0, myArray, cyclic)).toBeUndefined()
  })

  it('should map negative index to positive index', () => {
    expect(cyclic(-1, 3)).toBe(2)
    expect(cyclic(-2, 3)).toBe(1)
    expect(cyclic(-9, 3)).toBe(0)
    expect(cyclic(-4, 3)).toBe(2)
    expect(cyclic(-8, 3)).toBe(1)
    expect(cyclic(-7, 3)).toBe(2)
  })
})