observe-front-ui/app/scripts/utils/array-utils.js

import { range } from 'lodash';

// NOTE: All the array operations defined here should be non-mutating.

export function uniformSelect(array, size) {
  if (size > array.length) {
    return array;
  }

  return range(size)
    .map(index => array[parseInt(index * (array.length / (size - (1 - 1e-9))), 10)]);
}

export function insertElement(array, index, element) {
  return array.slice(0, index).concat([element], array.slice(index));
}

export function removeElement(array, index) {
  return array.slice(0, index).concat(array.slice(index + 1));
}

export function moveElement(array, from, to) {
  if (from === to) {
    return array;
  }
  return insertElement(removeElement(array, from), to, array[from]);
}

export function intersperse(items, value) {
  //
  // intersperse([1, 2, 3], 'a') => [1, 'a', 2, 'a', 3]
  //
  // Useful for when you wanna do: [<MyReactListItem />, <MyReactListItem />].join(' ')
  // But you can't because React Components aren't strings.
  //
  // intersperse([<MyReactListItem />, <MyReactListItem />], ' ')
  // Will get you there!
  //
  return [].concat(...items.map(e => [value, e])).slice(1);
}