// positive lookahead test
        const plaMatch = /foo(?=bar)/g.exec('foobar foobaz');
        console.assert(plaMatch != null, "Positive lookahead failed!") // PASS

        // negative lookahead test
        const nlaMatch = /foo(?!bar)/g.exec('foobar foobaz');
        console.assert(nlaMatch != null, "Negative lookahead failed!") // PASS

        // positive lookbehind test
        const plbMatch = /(?<=foo)bar/g.exec('foobar fuubar');
        console.assert(plbMatch != null, "Positive lookbehind failed!") // FAILED!

        // negative lookbehind test
        const nlbMatch = /(?<!foo)bar/g.exec('foobar fuubar');
        console.assert(nlbMatch != null, "Negative lookbehind failed!") // FAILED!