2nd/10_Wiki/Topic_JavaScript/JavaScript_Async_Await.md

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id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
javascript-async-await	JavaScript Async Await	Frontend	draft	conceptual		async await await keyword async function try catch await Promise.all		B	0.89	2026-06-23	2026-06-23			javascript js web frontend w3schools async-await promises	https://www.w3schools.com/js/js_async_await.asp

JavaScript Async Await

🎯 한 줄 통찰 (One-line insight)

async and await make promises easier by letting you write asynchronous code like normal step-by-step code, with familiar try...catch error handling. [S1]

🧠 핵심 개념 (Core concepts)

• They simplify promises — async and await make promises easier by letting code be written like normal step-by-step code. [S1]
• async returns a promise — an async function returns a promise; its return value is what the promise resolves to. [S1]
• await unwraps a promise — await pauses inside the async function until the awaited promise resolves, giving back the value directly. [S1]
• Error handling with try...catch — wrap awaited calls in try { ... } catch (error) { ... } to handle rejections. [S1]
• Sequential vs parallel — awaiting one call after another runs them in sequence; Promise.all([...]) runs them together and awaits all. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Linearize a promise chain — replace .then() chaining with successive await calls inside an async function. [S1]
• try/catch around await — catch a rejected promise (e.g. await fail()) like a synchronous error. [S1]
• Promise.all for parallelism — start promises first, then await Promise.all([p1, p2]) to collect results together. [S1]

📖 세부 내용 (Details)

Promises approach (before) [S1]

// Three functions to run in steps
function step1() {
  return Promise.resolve("A");
}
function step2(value) {
  return Promise.resolve(value + "B");
}
function step3(value) {
  return Promise.resolve(value + "C");
}

// Run the three functions in steps
step1()
.then(function(value) {
  return step2(value);
})
.then(function(value) {
  return step3(value);
})
.then(function(value) {
  myDisplayer(value);
});

async/await approach (after) The same logic reads like sequential code: [S1]

// Function to run the three functions in steps
async function run() {
  let v1 = await step1();
  let v2 = await step2(v1);
  let v3 = await step3(v2);
  myDisplayer(v3);
}

run();

The async keyword An async function returns a promise: [S1]

async function myFunction() {
  return "Hello";
}
myFunction().then(
  function(value) {myDisplayer(value);}
);

The await keyword await waits for a promise and returns its resolved value: [S1]

function step1() {
  return Promise.resolve("A");
}

async function run() {
  let value = await step1();
  myDisplayer(value);
}

run();

Error handling with try...catch [S1]

function fail() {
  return Promise.reject("Failed");
}

async function run() {
  try {
    let value = await fail();
    console.log(value);
  } catch (error) {
    console.log(error);
  }
}

run();

Sequential execution [S1]

async function run() {
  let a = await step1();
  let b = await step2();
  console.log(a, b);
}

Parallel with Promise.all() Start the promises first, then await them together: [S1]

async function run() {
  let p1 = step1();
  let p2 = step2();
  let values = await Promise.all([p1, p2]);
  console.log(values);
}

fetch() with async/await [S1]

async function loadData() {
  try {
    let response = await fetch("data.json");
    let data = await response.json();
    console.log(data);
  } catch (error) {
    console.log(error);
  }
}

loadData();

Basic syntax with a Promise Awaiting a constructed promise: [S1]

async function myDisplay() {
  let myPromise = new Promise(function(resolve, reject) {
    resolve("I love You !!");
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();

Without the reject parameter: [S1]

async function myDisplay() {
  let myPromise = new Promise(function(resolve) {
    resolve("I love You !!");
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();

Waiting for a timeout [S1]

async function myDisplay() {
  let myPromise = new Promise(function(resolve) {
    setTimeout(function() {resolve("I love You !!");}, 3000);
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();

🛠️ 적용 사례 (Applied in summary)

The page's snippets — the run() function linearizing step1/step2/step3, the try...catch around await fail(), and await Promise.all([p1, p2]) — are the canonical applied examples. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Linearize a chain with await (language: JavaScript):

async function run() {
  let v1 = await step1();
  let v2 = await step2(v1);
  let v3 = await step3(v2);
  myDisplayer(v3);
}

run();

Error handling and parallelism:

async function run() {
  try {
    let values = await Promise.all([step1(), step2()]);
    console.log(values);
  } catch (error) {
    console.log(error);
  }
}

⚖️ 비교 및 선택 기준 (Comparison & decision criteria)

• Promise .then() chaining — explicit, but reads as nested handler functions and requires returning each step. [S1]
• async/await — the same logic written like normal step-by-step code, with try...catch for errors; recommended for readability. Use sequential await for dependent steps and Promise.all for independent ones. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source.

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.89
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Promise, JavaScript Async Fetch, JavaScript Async Callbacks, JavaScript Async Debug
• 참조 맥락: The syntactic sugar over promises that most modern async data-fetching code uses.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript Async Await — https://www.w3schools.com/js/js_async_await.asp

📝 변경 이력 (Change history)

• 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Async Await" page (Astra wiki-curation, P-Reinforce v3.1 format).