{"type":"doc","content":[{"type":"heading","attrs":{"textAlign":null,"level":2},"content":[{"type":"text","text":"Базовый синтаксис"}]},{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","marks":[{"type":"bold"}],"text":"Обычная функция:"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"function getUser(): Promise<{ id: number; name: string }> {\n return fetch(\"/api/user\")\n .then(r => r.json()); // тип T = { id: number; name: string }\n}\n"}]},{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","marks":[{"type":"code"}],"text":"async"},{"type":"text","marks":[{"type":"bold"}],"text":"-функция (сахар):"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"async function getUser(): Promise<{ id: number; name: string }> {\n const r = await fetch(\"/api/user\");\n return r.json();\n}\n"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","text":"У "},{"type":"text","marks":[{"type":"code"}],"text":"async"},{"type":"text","text":" TypeScript сам выводит "},{"type":"text","marks":[{"type":"code"}],"text":"Promise"},{"type":"text","text":" по "},{"type":"text","marks":[{"type":"code"}],"text":"return"},{"type":"text","text":". Экспортируемые функции лучше "},{"type":"text","marks":[{"type":"bold"}],"text":"аннотировать явно"},{"type":"text","text":"."}]}]},{"type":"horizontalRule"},{"type":"heading","attrs":{"textAlign":null,"level":2},"content":[{"type":"text","text":"Частые варианты"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"async function ping(): Promise {\n await fetch(\"/ping\"); // ничего не возвращаем\n}\n\nfunction loadIds(): Promise {\n return fetch(\"/ids\").then(r => r.json());\n}\n\nasync function isOk(): Promise {\n const r = await fetch(\"/health\");\n return r.ok;\n}\n"}]},{"type":"horizontalRule"},{"type":"heading","attrs":{"textAlign":null,"level":2},"content":[{"type":"text","text":"Generic-функции"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"async function getJSON(url: string, init?: RequestInit): Promise {\n const r = await fetch(url, init);\n if (!r.ok) throw new Error(`HTTP ${r.status}`);\n return r.json() as Promise;\n}\n\n// Использование\nconst user = await getJSON<{ id: number; name: string }>(\"/api/user\");\n"}]},{"type":"horizontalRule"},{"type":"heading","attrs":{"textAlign":null,"level":2},"content":[{"type":"text","text":"Ошибки и "},{"type":"text","marks":[{"type":"code"}],"text":"catch"}]},{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","text":"У промисов "},{"type":"text","marks":[{"type":"bold"}],"text":"тип отказа не аннотируется"},{"type":"text","text":" (TypeScript не знает «тип ошибки»). В "},{"type":"text","marks":[{"type":"code"}],"text":"catch"},{"type":"text","text":" используйте "},{"type":"text","marks":[{"type":"code"}],"text":"unknown"},{"type":"text","text":" и сужение:"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"try {\n await getUser();\n} catch (e: unknown) {\n if (e instanceof Error) console.error(e.message);\n}\n"}]},{"type":"horizontalRule"},{"type":"heading","attrs":{"textAlign":null,"level":2},"content":[{"type":"text","text":"Полезные утилиты"}]},{"type":"bulletList","content":[{"type":"listItem","content":[{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","marks":[{"type":"code"}],"text":"Awaited"},{"type":"text","text":" — «распаковать» промис:"}]},{"type":"codeBlock","attrs":{"language":"javascript"},"content":[{"type":"text","text":"type User = Awaited>; // { id: number; name: string }\n"}]}]},{"type":"listItem","content":[{"type":"paragraph","attrs":{"textAlign":null},"content":[{"type":"text","marks":[{"type":"code"}],"text":"PromiseSettledResult"},{"type":"text","text":" для "},{"type":"text","marks":[{"type":"code"}],"text":"Promise.allSettled"},{"type":"text","text":"."}]}]}]},{"type":"paragraph","attrs":{"textAlign":null}}]}

Типизация асинхронных функций

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