ES2026의 새 JavaScript 기능 7가지 (그리고 아직 기다리는 2가지)

const opinions = new Map();

function addOpinion(topic, author) {
  if (!opinions.has(topic)) {
    opinions.set(topic, []);
  }

  opinions.get(topic).push(author);
}

addOpinion("React is dead", "10x Engineer");
addOpinion("React is dead", "Principal AI Evangelist");

const opinions = new Map();

opinions
  .getOrInsert("React is dead", [])
  .push("10x Engineer");

opinions
  .getOrInsert("React is dead", [])
  .push("Principal AI Evangelist");

console.log(opinions);

const opinions = new Map();

opinions
  .getOrInsertComputed(
    "Nobody writes clean code anymore",
    () => []
  )
  .push("DDD Purist");

const posts = [
  "Angular is dead",
  "JavaScript was a mistake"
];

const iterator = posts.values();

console.log(iterator.next());
// { value: "Angular is dead", done: false }

console.log(iterator.next());
// { value: "JavaScript was a mistake", done: false }

console.log(iterator.next());
// { value: undefined, done: true }

function* endlessHotTakes() {
  while (true) {
    yield "Everything should be rewritten in Rust.";
  }
}

const iterator = endlessHotTakes();

console.log(iterator.next().value);
console.log(iterator.next().value);
console.log(iterator.next().value);

function* linkedinFeed() {
  yield "Use Rust for everything";
  yield "JavaScript was a mistake";
  yield "Clean code is dead";
  yield "Angular is dead";
}

const controversialTakes =
  linkedinFeed()
    .filter(post => post.includes("dead"))
    .map(post => `🔥 ${post}`);

console.log([...controversialTakes]);

function* frontendExperts() {
  yield "React is dead";
  yield "Nobody needs Redux";
}

function* backendExperts() {
  yield "Microservices solve everything";
  yield "Frontend developers don't understand architecture";
}

const feed = Iterator.concat(
  frontendExperts(),
  backendExperts()
);

console.log([...feed]);

async function* angryComments() {
  yield "This could have been a plain HTML form.";
  yield "Angular is dead.";
  yield "React is dead.";
  yield "JavaScript was a mistake.";
}

const comments = await Array.fromAsync(
  angryComments()
);

console.log(comments); 
// This could have been a plain HTML form.
// Angular is dead.
// etc

const opinions = [
  Promise.resolve("Nobody should use classes."),
  Promise.resolve("Signals change everything."),
  Promise.resolve("Microservices ruined software.")
];

const takes = await Array.fromAsync(opinions);

console.log(takes); 

const comments = await Array.fromAsync(
  angryComments(),
  opinion => opinion.toUpperCase()
);

console.log(comments);

console.log(0.1 + 0.2);
// 0.30000000000000004

const productivityBoosts = [
  0.1, // cold showers
  0.2, // AI agents
  0.3, // journaling
  0.4, // waking up at 4 AM
];

console.log(
  Math.sumPrecise(productivityBoosts)
);

try {
  throw new Error(
    "Angular is dead."
  );
}
catch (e) {

  console.log(
    e instanceof Error
  );
}

const strangeThing =
  window.frames[0].eval(
    "new Error('JavaScript was a mistake.')"
  );

console.log(
  strangeThing instanceof Error
);

// false 

console.log(
  Error.isError(strangeThing)
);

// true

btoa("JavaScript was a mistake.");

const bytes = new Uint8Array(buffer);

const base64 = btoa(
  String.fromCharCode(...bytes)
);

const screenshot =
  await fetch(
    "/proof/react-is-dead.png"
  );

const bytes =
  new Uint8Array(
    await screenshot.arrayBuffer()
  );

const base64 =
  bytes.toBase64();

console.log(base64);

const json = `
{
  "followers":
  999999999999999999999999999999
}
`;

const data = JSON.parse(json);

console.log(data.followers);

const data = JSON.parse(
  json,
  (key, value, context) => {

    if (key === "followers") {
      return BigInt(context.source);
    }

    return value;
  }
);

console.log(data.followers);

const date = new Date("2026-03-30");

console.log(date);

const today = new Date();

today.setMonth(today.getMonth() + 1);

const now = Temporal.Now.instant();

const birthday =
  Temporal.PlainDate.from(
    "1987-07-23"
  );

const meeting =
  Temporal.ZonedDateTime.from(
    "2026-11-03T10:00:00[Europe/Warsaw]"
  );

const webinar =
  createAIAgentsWebinar();

try {

  webinar.start();

}
finally {

  webinar.close();

}

using webinar =
  createAIAgentsWebinar();

webinar.start();