timeline
    title JavaScript Evolution
    ES6 (2015) : let/const, arrow functions, classes, promises, modules, template literals, destructuring, spread/rest, Map/Set, Symbol, proxies
    ES7 (2016) : Array.includes, exponentiation operator (**)
    ES8 (2017) : async/await, Object.values, Object.entries, String.padStart, trailing commas
    ES9 (2018) : rest/spread for objects, async iteration, Promise.finally
    ES10 (2019) : Array.flat, Array.flatMap, Object.fromEntries, String.trimStart/trimEnd
    ES11 (2020) : nullish coalescing (??), optional chaining (?.), globalThis, BigInt, Promise.allSettled
    ES12 (2021) : String.replaceAll, Promise.any, logical assignment (&&=, ||=, ??=)
    ES13 (2022) : Array.at, Error cause, top-level await, private class fields (#)
    ES14 (2023) : Array findLast, Array toReversed/toSorted/toSpliced