Simple calculator

add.js

Calculator.prototype.add = function () {
    var result = 0;
    for (var i = 0, j = arguments.length; i < j; i++) {
        result += parseFloat(arguments[i]);
    }
    return result;
};

calcultor.js

function Calculator() {
}

subtract.js

Calculator.prototype.subtract = function () {
    var result = 0;
    if (arguments.length > 0) result = arguments[0];
    for (var i = 1, j = arguments.length; i < j; i++) {
        result -= parseFloat(arguments[i]);
    }
    return result;
};