Poor man's option type

options.js

/*
Usage example

option(document.findElementById('header'))
    .map(function (header) {
        header.textContent = 'Uh oh';
    })
    .orElse(function () {
        document.body.insertAdjacentHTML('afterbegin', '<h1 id="header">Uh oh</h1>');
    });

*/

var option = function (obj) {
    return {
        map: function (fn, thisArg) {
            if (obj) {
                fn.call(thisArg, obj);
            }

            return {
                orElse: function (fn, thisArg) {
                    if (!obj) {
                        fn.call(thisArg);
                    }
                }
            }
        }
    }
}

// https://igor.io/2014/01/10/functional-library-null.html
// https://github.com/schmittjoh/php-option
// https://github.com/pr1001/option.js
// https://github.com/commuterjoy/js-scala-option
// https://github.com/shinypb/option.js