---
title: pluralize
tags: string,advanced
firstSeen: 2018-01-03T13:17:19+02:00
lastUpdated: 2020-10-22T20:24:04+03:00
---

Returns the singular or plural form of the word based on the input number, using an optional dictionary if supplied.

- Use a closure to define a function that pluralizes the given `word` based on the value of `num`.
- If `num` is either `-1` or `1`, return the singular form of the word.
- If `num` is any other number, return the `plural` form.
- Omit the third argument, `plural`, to use the default of the singular word + `s`, or supply a custom pluralized `word` when necessary.
- If the first argument is an `object`, return a function which can use the supplied dictionary to resolve the correct plural form of the word.

```js
const pluralize = (val, word, plural = word + 's') => {
  const _pluralize = (num, word, plural = word + 's') =>
    [1, -1].includes(Number(num)) ? word : plural;
  if (typeof val === 'object')
    return (num, word) => _pluralize(num, word, val[word]);
  return _pluralize(val, word, plural);
};
```

```js
pluralize(0, 'apple'); // 'apples'
pluralize(1, 'apple'); // 'apple'
pluralize(2, 'apple'); // 'apples'
pluralize(2, 'person', 'people'); // 'people'

const PLURALS = {
  person: 'people',
  radius: 'radii'
};
const autoPluralize = pluralize(PLURALS);
autoPluralize(2, 'person'); // 'people'
```