Found this code to pluralize words, nouns to be exact. It included some functions that where not defined so I've added the var 'last' to replace the original function that grabbed the last character.

Plurilization of words

String.prototype.plural = function () {
	// last character
	var last = this.charAt(this.length-1);

	if (this.last === 'y') {
		if ( (this.charAt(this.length - 2)).isVowel() ) {
			// If the y has a vowel before it (i.e. toys), then you just add the s. 
			return this + 's';
		}
		else {
			// If a this ends in y with a consonant before it (fly), you drop the y and add -ies to make it plural. 
			return this.slice(0, -1) + 'ies';
		}
	}
	else if (this.substring( this.length - 2) === 'us') {				
		// ends in us -> i, needs to preceed the generic 's' rule
		return this.slice(0, -2) + 'i'; 
	}
	else if (['ch', 'sh'].indexOf(this.substring( this.length - 2)) !== -1 || ['x','s'].indexOf(last) !== -1) {
	 	// If a this ends in ch, sh, x, s, you add -es to make it plural.
		return this + 'es';
	}
	else {
		// anything else, just add s			
		return this + 's';
	}
}

// use like this
console.log(somenoun.plural());