Get a date with an offset in JS

get-date-with-offset.js

'use strict';

var getDateWithOffset = function getDateWithOffset(date, offset) {
    if (!(date instanceof Date)) {
        throw new TypeError('The parameter "date" must be a Date object.');
    }

    if (typeof offset !== 'number') {
        throw new TypeError('The parameter "offset" must be a number.');
    }

    var localTime = date.getTime();
    var localOffset = date.getTimezoneOffset() * 60000;
    var utcTime = localTime + localOffset;
    var distantTime = utcTime + (3600000 * offset);

    return new Date(distantTime);
};

// Ex: var paris = getDateWithOffset(new Date(), +2);