typescript-expert

TypeScript Expert (TypeScript 5.8+ Edition)

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English

Orchestration & Integration

Connects and orchestrates with relevant domain skills like brainstorming, zero-to-prod-orchestrator, and project-context-mapper to ensure cohesive execution.

Description

Expert-level TypeScript development covering the advanced type system, strict mode enforcement, generic programming, utility types, branded types, and type-safe patterns for production applications. Targets TypeScript 5.8+ features including inferred type predicates, isolated declarations, NoInfer, using declarations, variadic tuple improvements, and const type parameters.

Trigger Conditions

• Writing TypeScript with advanced generic constraints.
• Enforcing strict type safety in existing codebases.
• Designing type-safe API contracts (REST, tRPC, Zod schemas).
• Implementing branded types for domain modeling.
• Resolving complex type errors or any pollution.
• Setting up tsconfig.json for strict projects.
• Writing TypeScript utility types or type helpers.

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TypeScript 5.x — Key Features

using Declarations (Explicit Resource Management, TS 5.2)

// Automatically calls [Symbol.dispose] on scope exit
function processFile(path: string) {
  using handle = openFile(path); // disposed when function exits
  handle.write('data');
}

// Async version with [Symbol.asyncDispose]
async function processDatabase() {
  await using conn = await getConnection();
  await conn.query('SELECT 1');
} // conn.close() called automatically

NoInfer<T> Utility Type (TS 5.4)

// Prevents unintended type widening in generic inference
function createState<T>(initial: T, fallback: NoInfer<T>): T {
  return initial ?? fallback;
}

// TS now errors if fallback type doesn't match initial
createState('hello', 42); // Error: Argument of type 'number' is not assignable to type 'string'