Ramda Adjunct 2.30.0

isSparseArray.js

  1. import {
  2.   values,
  3.   both,
  4.   complement,
  5.   pipe,
  6.   converge,
  7.   identical,
  8.   length,
  9. } from 'ramda';
  11. import isArray from './isArray';
  13. /**
  14.  * Checks if input value is a sparse Array.
  15.  * An array with at least one "empty slot" in it is often called a "sparse array."
  16.  * Empty slot doesn't mean that the slot contains `null` or `undefined` values,
  17.  * but rather that the slots don't exist.
  18.  *
  19.  * @func isSparseArray
  20.  * @memberOf RA
  21.  * @since {@link https://char0n.github.io/ramda-adjunct/2.20.0|v2.20.0}
  22.  * @category Type
  23.  * @sig * -> Boolean
  24.  * @param {*} list The list to test
  25.  * @return {boolean}
  26.  * @see {@link https://github.com/getify/You-Dont-Know-JS/blob/f0d591b6502c080b92e18fc470432af8144db610/types%20%26%20grammar/ch3.md#array|Sparse Arrays}, {@link RA.isArray|isArray}
  27.  * @example
  28.  *
  29.  * RA.isSparseArray(new Array(3)); // => true
  30.  * RA.isSparseArray([1,,3]); // => true
  31.  *
  32.  * const list = [1, 2, 3];
  33.  * delete list[1];
  34.  * RA.isSparseArray(list); // => true
  35.  *
  36.  * RA.isSparseArray([1, 2, 3]); // => false
  37.  */
  38. const isSparseArray = both(
  39.   isArray,
  40.   converge(complement(identical), [pipe(values, length), length])
  41. );
  43. export default isSparseArray;