pluralize.js

String.prototype.plural = function () {
	if (this.lastChar() === '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(this.lastChar()) !== -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';
	}
}