Explain the relationship between TypeScript and ECMAScript proposals.

TypeScript often implements stage 3+ proposals early, providing feedback to TC39. Some features like decorators evolved differently than proposals. TypeScript's Role in ECMAScript Evolution: • TypeScript team participates in TC39 committee • Implements experimental features for community feedback • Provides real-world usage data for proposals • Sometimes influences proposal direction Stage-based Implementation: Stage 0-1: Strawman/Proposal - TypeScript rarely implements these - Too early and unstable Stage 2: Draft - TypeScript may implement with experimental flag - Helps gather community feedback Stage 3: Candidate - TypeScript often implements these - Likely to become standard - Examples: Optional chaining, nullish coalescing Stage 4: Finished - TypeScript implements quickly - Becomes part of standard JavaScript Notable Examples: Optional Chaining (Stage 4): // TypeScript implemented early const user = response?.data?.user?.name; Nullish Coalescing (Stage 4): // TypeScript supported before browsers const config = userConfig ?? defaultConfig; Decorators (Stage 2): // TypeScript has own implementation @Component class MyComponent {} Private Fields (Stage 4): // TypeScript supported with # syntax class User { #id: number; constructor(id: number) { this.#id = id; } } Top-Level Await (Stage 4): // TypeScript supported in modules const data = await fetch('/api/data'); Divergent Evolution: Decorators: - TypeScript implemented experimental version - TC39 proposal evolved differently - TypeScript now supports both versions Modules: - TypeScript had own module system - ES6 modules became standard - TypeScript adapted to support both Configuration for Proposals: { "compilerOptions": { "target": "ES2022", "experimentalDecorators": true, "emitDecoratorMetadata": true, "useDefineForClassFields": true } } Benefits: • Early access to future JavaScript features • Community feedback shapes proposals • Smooth transition when features standardize • TypeScript helps validate proposal viability.