TypeScript 5.5+: 격리된 선언과 그 이후

TypeScript 5.5 개요

// npm install typescript@5.5

추론된 타입 술어

// Before 5.5: had to annotate manually
function isString(val: unknown): val is string {
  return typeof val === "string";
}

// After 5.5: TypeScript infers the predicate automatically
function isString(val: unknown) {
  return typeof val === "string";
}
// Inferred: (val: unknown) => val is string

isolatedDeclarations: 참

{
  "compilerOptions": {
    "isolatedDeclarations": true
  }
}
// Exported functions without return types now cause an error

정규 표현식 구문 검사

const re = /(?<name>\w+)/; // OK — named capture group
const bad = /[z-a]/;        // Error: invalid character class range

상수 인덱스의 제어 흐름 타입 좁히기

const obj = { x: Math.random() > 0.5 ? "a" : "b" };
if (obj.x === "a") {
  // TS 5.5: obj.x is narrowed to "a" here
  console.log(obj.x.toUpperCase());
}

TypeScript 5.6과 그 이후

# Quarterly release cadence:
# 5.5: June 2024
# 5.6: September 2024
# 5.7: December 2024
# 5.8: March 2025

TypeScript 로드맵 살펴보기

# TypeScript iteration plans:
# github.com/microsoft/TypeScript/issues?q=Iteration+Plan

ECMAScript와의 호환

# TC39 proposals: https://tc39.es/proposals/
# Stage 3 = TypeScript eligible for inclusion

TypeScript 안전하게 업그레이드하기

npm install typescript@latest
npx tsc --noEmit
# Review: https://www.typescriptlang.org/docs/handbook/release-notes/overview.html

@typescript/nightly로 최신 상태 유지하기

npm install typescript@next
# Use nightly in a separate branch or experimental project

커뮤니티 리소스

# Resources:
# typescriptlang.org/docs
# devblogs.microsoft.com/typescript
# totaltypescript.com
# discord.gg/typescript

복습: TypeScript 5.5 이상

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