Based on @pmrotule answer with some typescript magic and some additions to the uncountable array. I add here the plural and singular functions.
The plural version:
/**
* Returns the plural of an English word.
*
* @export
* @param {string} word
* @param {number} [amount]
* @returns {string}
*/
export function plural(word: string, amount?: number): string {
if (amount !== undefined && amount === 1) {
return word
}
const plural: { [key: string]: string } = {
'(quiz)$' : "$1zes",
'^(ox)$' : "$1en",
'([m|l])ouse$' : "$1ice",
'(matr|vert|ind)ix|ex$' : "$1ices",
'(x|ch|ss|sh)$' : "$1es",
'([^aeiouy]|qu)y$' : "$1ies",
'(hive)$' : "$1s",
'(?:([^f])fe|([lr])f)$' : "$1$2ves",
'(shea|lea|loa|thie)f$' : "$1ves",
'sis$' : "ses",
'([ti])um$' : "$1a",
'(tomat|potat|ech|her|vet)o$': "$1oes",
'(bu)s$' : "$1ses",
'(alias)$' : "$1es",
'(octop)us$' : "$1i",
'(ax|test)is$' : "$1es",
'(us)$' : "$1es",
'([^s]+)$' : "$1s"
}
const irregular: { [key: string]: string } = {
'move' : 'moves',
'foot' : 'feet',
'goose' : 'geese',
'sex' : 'sexes',
'child' : 'children',
'man' : 'men',
'tooth' : 'teeth',
'person' : 'people'
}
const uncountable: string[] = [
'sheep',
'fish',
'deer',
'moose',
'series',
'species',
'money',
'rice',
'information',
'equipment',
'bison',
'cod',
'offspring',
'pike',
'salmon',
'shrimp',
'swine',
'trout',
'aircraft',
'hovercraft',
'spacecraft',
'sugar',
'tuna',
'you',
'wood'
]
// save some time in the case that singular and plural are the same
if (uncountable.indexOf(word.toLowerCase()) >= 0) {
return word
}
// check for irregular forms
for (const w in irregular) {
const pattern = new RegExp(`${w}$`, 'i')
const replace = irregular[w]
if (pattern.test(word)) {
return word.replace(pattern, replace)
}
}
// check for matches using regular expressions
for (const reg in plural) {
const pattern = new RegExp(reg, 'i')
if (pattern.test(word)) {
return word.replace(pattern, plural[reg])
}
}
return word
}
And the singular version:
/**
* Returns the singular of an English word.
*
* @export
* @param {string} word
* @param {number} [amount]
* @returns {string}
*/
export function singular(word: string, amount?: number): string {
if (amount !== undefined && amount !== 1) {
return word
}
const singular: { [key: string]: string } = {
'(quiz)zes$' : "$1",
'(matr)ices$' : "$1ix",
'(vert|ind)ices$' : "$1ex",
'^(ox)en$' : "$1",
'(alias)es$' : "$1",
'(octop|vir)i$' : "$1us",
'(cris|ax|test)es$' : "$1is",
'(shoe)s$' : "$1",
'(o)es$' : "$1",
'(bus)es$' : "$1",
'([m|l])ice$' : "$1ouse",
'(x|ch|ss|sh)es$' : "$1",
'(m)ovies$' : "$1ovie",
'(s)eries$' : "$1eries",
'([^aeiouy]|qu)ies$' : "$1y",
'([lr])ves$' : "$1f",
'(tive)s$' : "$1",
'(hive)s$' : "$1",
'(li|wi|kni)ves$' : "$1fe",
'(shea|loa|lea|thie)ves$': "$1f",
'(^analy)ses$' : "$1sis",
'((a)naly|(b)a|(d)iagno|(p)arenthe|(p)rogno|(s)ynop|(t)he)ses$': "$1$2sis",
'([ti])a$' : "$1um",
'(n)ews$' : "$1ews",
'(h|bl)ouses$' : "$1ouse",
'(corpse)s$' : "$1",
'(us)es$' : "$1",
's$' : ""
}
const irregular: { [key: string]: string } = {
'move' : 'moves',
'foot' : 'feet',
'goose' : 'geese',
'sex' : 'sexes',
'child' : 'children',
'man' : 'men',
'tooth' : 'teeth',
'person' : 'people'
}
const uncountable: string[] = [
'sheep',
'fish',
'deer',
'moose',
'series',
'species',
'money',
'rice',
'information',
'equipment',
'bison',
'cod',
'offspring',
'pike',
'salmon',
'shrimp',
'swine',
'trout',
'aircraft',
'hovercraft',
'spacecraft',
'sugar',
'tuna',
'you',
'wood'
]
// save some time in the case that singular and plural are the same
if (uncountable.indexOf(word.toLowerCase()) >= 0) {
return word
}
// check for irregular forms
for (const w in irregular) {
const pattern = new RegExp(`${irregular[w]}$`, 'i')
const replace = w
if (pattern.test(word)) {
return word.replace(pattern, replace)
}
}
// check for matches using regular expressions
for (const reg in singular) {
const pattern = new RegExp(reg, 'i')
if (pattern.test(word)) {
return word.replace(pattern, singular[reg])
}
}
return word
}