2019 and later
Each solution is a module export in js/dayX.js which returns an array of part1 and part2 answers.
It includes a runner: node 2020 1 to just get the answer. node 2020 1 bench to benchmark the solution.
2018 and earlier
Daily solutions are added to window.AdventOfCode namespace, and are available under methods like Day1, Day2, etc.
Each method returns an array of two elements: solution to part one and two.