const values = [1, 2, 3, 'a', 'b', 'c'];

// [] -> []
// [x] -> [x]
// x: xs : y -> [x, y] ++ func(xs)
const melder = values => {
    if (values.length <= 1) {
        return values;
    }

    const head = values[0];
    const tail = values[values.length - 1];
    const body = values.slice(1, values.length - 1);

    return [head, tail].concat(melder(body));
};

const res = melder(values);
console.log('res', res);