StringCalculator with and without underscore.js

stringcalculator_v1.js

StringCalculator = {
	add : function(input) {
		checkIfContainsNegativeNumbers(input);
		var parser = new Parser(input);
		var numbers = parser.parse();
		return numbers.getSummatory();
	}
}

function checkIfContainsNegativeNumbers(input) {
	negativeNumbers = input.getNegativeNumbers();
	if (negativeNumbers) 
		throw "Negative numbers are not supported (" + negativeNumbers.toStringList() + ")";
}

function Parser(input) {

	var _input = input;

	this.parse = function() {
		var separator = parseSeparator(_input);
		var numbers = parseNumbers(_input);
		return numbers.replace(separator, ",").split(/,|\n/g);
	}

	function parseNumbers(input) {
		if (input.hasCustomDelimiter())
			return input.getNumbersAfterDelimiterDefinition(); 

		return input;
	}

	function parseSeparator(input) {
		if (input.hasCustomDelimiter())
			return input.getCustomDelimiter();

		return ",";
	}

}

/* Extending Javascript types to symplify code legibility */

Array.prototype.getSummatory = function() {
	var result = 0;
	for (var current = 0; current < this.length; current++) 
		result += parseInt(this[current] || 0);
	return result;
}

Array.prototype.toStringList = function() {
	var message = "";
	for (var current = 0; current < this.length; current++) {
		message += this[current];
		if (current < this.lastElementPosition())
			message += ", ";
	}
	return message;
}

Array.prototype.lastElementPosition = function() {
	return this.length - 1;
}

String.prototype.getNegativeNumbers = function() {
	return this.match(/-\d/g);
}

String.prototype.hasCustomDelimiter = function() {
	return this.match("^\/\/");
}

String.prototype.getCustomDelimiter = function() {
	return this.charAt(2);
}

String.prototype.getNumbersAfterDelimiterDefinition = function() {
	var matcher = this.match("(//;\n)?(.*)");
	return matcher[2];
}

stringcalculator_v2.js

StringCalculator = {
	add : function(input) {
		checkIfContainsNegativeNumbers(input);
		var numbers = new Parser(input).parse();
		return _(numbers).reduce(this.summatory);
	},
	
	summatory: function(summatory, element) {
		return summatory + element;
	}
}

function checkIfContainsNegativeNumbers(input) {
	negativeNumbers = input.getNegativeNumbers();
	if (negativeNumbers) 
		throw "Negative numbers are not supported (" + negativeNumbers.toString() + ")";
}

function Parser(input) {
	
	var _input = input;
	
	this.parse = function() {
		var separator = parseSeparator(_input);
		var numbers = parseNumbers(_input);
		numbers = numbers.replace(separator, ",").split(/,|\n/g);
		return _(numbers).map(parseToIntNumber);
	}
	
	function parseNumbers(input) {
		if (input.hasCustomDelimiter())
			return input.getNumbersAfterDelimiterDefinition(); 
			
		return input;
	}
	
	function parseSeparator(input) {
		if (input.hasCustomDelimiter())
			return input.getCustomDelimiter();
		
		return ",";
	}
	
 	var parseToIntNumber = function(element) {
		return parseInt(element || 0);
	}
	
}

/* Extending Javascript types to symplify code legibility */

String.prototype.getNegativeNumbers = function() {	
	return this.match(/-\d/g);
}

String.prototype.hasCustomDelimiter = function() {
	return this.match("^\/\/");
}

String.prototype.getCustomDelimiter = function() {
	return this.charAt(2);
}

String.prototype.getNumbersAfterDelimiterDefinition = function() {
	var matcher = this.match("(//;\n)?(.*)");
	return matcher[2];
}