JavaScript Developer Job Description Template (2026)

Full JD (copy-ready)

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# JavaScript Developer — Job Description

## Role summary
A JavaScript Developer builds and maintains features across our stack: browser UI, Node services, and the tooling between them. They write modern, typed JavaScript, handle async flows correctly, keep the build fast, and turn product requirements into shipped, tested code that works in both the browser and on the server without a handoff between two specialists.

## Responsibilities
- Build new features across the JavaScript stack — browser UI, Node endpoints, and shared logic — in TypeScript against product specs.
- Write correct async code using promises, async/await, and AbortController, with error paths handled as carefully as the happy path.
- Add and tighten TypeScript types across the codebase, including generics and discriminated unions, and drive incremental JS-to-TS migration where needed.
- Own the build tooling — Vite, esbuild, or Webpack — including code splitting, environment config, and dependency and lockfile hygiene.
- Consume and shape REST or GraphQL APIs, validating input at the boundary and typing responses on the client.
- Write unit and integration tests in Vitest or Jest plus Playwright end-to-end tests for critical user paths.
- Debug across the browser/server boundary using DevTools, source maps, and Node inspector rather than guesswork.
- Configure and enforce ESLint and Prettier in CI so review stays focused on logic.
- Refactor legacy callback-heavy or untyped modules into readable, typed async code without changing behavior.
- Review pull requests for async correctness, type safety, and clarity, and leave feedback that unblocks the author.

## Must-have skills
- 3+ years shipping production JavaScript, with deep command of closures, prototypes, this-binding, and the event loop.
- Fluent in modern ES2023+ syntax and the browser DOM, events, and forms without a framework crutch.
- Strong async skills: promises, async/await, microtask vs macrotask ordering, cancellation, and error handling.
- Production TypeScript — able to add generics, model unions, and tighten types on existing untyped code.
- Comfortable in Node.js: an HTTP framework (Express, Fastify, or Nest), scripts, and the module system.
- Hands-on with a modern bundler (Vite, esbuild, or Webpack) and package managers (npm, pnpm, or Bun).
- Writes tests in Vitest or Jest and can read Playwright or Cypress output.
- Strong written English for async code review, spec docs, and Slack threads.

## Nice-to-have skills
- Depth in a UI framework (React, Vue, or Svelte) or a meta-framework (Next.js, Nuxt).
- Experience migrating a plain-JavaScript codebase to TypeScript incrementally.
- Monorepo tooling experience (Turborepo, Nx, or pnpm workspaces).
- Familiarity with GraphQL on both the server and the client.
- Contributions to an open-source JavaScript library or tool.

## Tools and technology
- JavaScript (ES2023+)
- TypeScript
- Node.js
- Vite / esbuild / Webpack
- Express / Fastify
- Vitest / Jest
- Playwright
- ESLint & Prettier
- npm / pnpm / Bun
- Git & GitHub Actions

## Reporting structure
Reports to the Engineering Manager or Tech Lead. Collaborates daily with product designers (Figma handoff), other engineers (API contracts and code review), QA, and the product manager for the feature area.

## Success metrics (KPIs)
- Weekly PR throughput and review turnaround on own and peer PRs.
- Production error rate (Sentry) trending flat or down quarter-over-quarter.
- Test coverage on behavioral paths maintained or improved each sprint.
- Build times and bundle budgets kept within target as the codebase grows.
- TypeScript strictness increased over time with fewer any escapes.
- Time-to-first-PR for the feature areas the developer owns.