source: trip-planner-front/node_modules/symbol-observable/es/ponyfill.js

export default function symbolObservablePonyfill(root) {
        var result;
        var Symbol = root.Symbol;

        if (typeof Symbol === 'function') {
                if (Symbol.observable) {
                        result = Symbol.observable;
                } else {

                        if (typeof Symbol.for === 'function') {
                                // This just needs to be something that won't trample other user's Symbol.for use
                                // It also will guide people to the source of their issues, if this is problematic.
                                // META: It's a resource locator!
                                result = Symbol.for('https://github.com/benlesh/symbol-observable');
                        } else {
                                // Symbol.for didn't exist! The best we can do at this point is a totally 
                                // unique symbol. Note that the string argument here is a descriptor, not
                                // an identifier. This symbol is unique.
                                result = Symbol('https://github.com/benlesh/symbol-observable');
                        }
                        try {
                                Symbol.observable = result;
                        } catch (err) {
                                // Do nothing. In some environments, users have frozen `Symbol` for security reasons,
                                // if it is frozen assigning to it will throw. In this case, we don't care, because
                                // they will need to use the returned value from the ponyfill.
                        }
                }
        } else {
                result = '@@observable';
        }

        return result;
};