What Is JavaScript and TypeScript Code Review?
JavaScript and TypeScript code review is the practice of checking changes to JavaScript or TypeScript code before they merge. Most teams run a JavaScript linter such as ESLint, a formatter and the TypeScript compiler first, then have a person or an AI reviewer read the change for logic, security and design.
TypeScript adds types to JavaScript, so the compiler catches many mistakes before review. Reviewers still check what types can’t: behavior, data flow and how the change fits the rest of the app.
What Changed in JavaScript and TypeScript Code Review in 2026
In 2026, the main JavaScript tools changed under teams’ feet, while JavaScript and TypeScript stayed the code most teams review.
TypeScript went native. TypeScript 7.0 is a port of the compiler to Go, and Microsoft says full builds are about 8 to 12 times quicker. Tools that need the compiler’s API, such as typescript-eslint, run alongside a TypeScript 6 package for now (July 8, 2026, TypeScript blog).
ESLint dropped its old config. ESLint v10 removed the legacy .eslintrc format, so every project now uses the flat eslint.config.js file (February 6, 2026, ESLint blog). ESLint v9 reached end of life on August 6, 2026 (ESLint).
JavaScript and TypeScript remain the code most teams review. In Stack Overflow’s 2026 survey, JavaScript was the most-used language for the 12th year (62.0%), and TypeScript ranked sixth (43.8%) (October 6, 2026, Stack Overflow).
Toolchain changes plus AI-written code mean review has to cover config, types and intent together.
What Reviewers Check in JavaScript and TypeScript Code
| Area | What reviewers look for | Example |
|---|---|---|
| Types | Real types instead of any and unsafe casts | as unknown as User hiding a shape mismatch |
| Async code | Promises awaited, errors caught and races avoided | A forEach with async callbacks that never wait |
| Null handling | undefined and null handled at the edges | Reading user.profile.name without a check |
| Security | User input kept out of HTML, queries and eval | innerHTML built from a URL parameter |
| Dependencies | New packages that are needed, maintained and safe | A large library added for one helper |
| Framework rules | Hooks, effects and state used correctly | A React effect missing a dependency |
What a JavaScript Linter Checks
A JavaScript linter reads code without running it and reports likely bugs and style problems. ESLint is the most used JavaScript linter, and typescript-eslint adds rules that use TypeScript’s type information.
| Tool | What it does | Typical use |
|---|---|---|
| ESLint | Reports bugs and style issues with configurable rules | Editor and CI |
| typescript-eslint | Adds type-aware rules to ESLint | TypeScript projects |
TypeScript compiler (tsc) | Checks types across the project | Build and CI |
| Prettier or another formatter | Formats code in one style | Save or commit |
What Linters Can’t Check in JavaScript and TypeScript Review
Linters and types check code against rules and shapes. Neither can tell whether a checkout flow charges the right amount, whether a new API call matches what the backend returns or whether a change breaks a shared package used by another app.
Questions like these need a reviewer who knows the codebase.
Qodo’s Take: Let ESLint Check the Code and Review Check the Change
JavaScript teams have deep linting, and TypeScript catches a lot. The gaps are behavior, team conventions and changes that ripple into other packages or services.
You shouldn’t review code with the same tool that wrote it. An agent that wrote an unsafe cast usually thinks the types are fine.
Choose Qodo if changes in one JavaScript or TypeScript repository keep breaking another. Qodo reviews pull requests in GitHub, GitLab, Bitbucket, Azure DevOps and Gerrit, separate from the agents that write the code.
Qodo is the best AI code review platform for JavaScript and TypeScript teams because it reviews each PR with full codebase context and the team’s own rules, while ESLint and the compiler keep handling known patterns and types.
Qodo Checks Your Team’s Frontend and Backend Rules
Once Rule enforcement is on (Beta, on GitHub, GitLab, Bitbucket Cloud and Azure DevOps), Qodo checks PRs against rules imported from files such as AGENTS.md or CLAUDE.md. A file such as apps/web/AGENTS.md applies only under that folder, so frontend and backend can keep different rules in one repository (last checked October 2026, Qodo’s docs).
See custom rules for code review.
Qodo Flags Changes That Break Shared Packages
Qodo’s Cross-repo findings, in Beta, flag a change that breaks code in a related repository, such as a renamed function in a shared library, once the repositories’ relationships are discovered or defined (last checked October 2026, Qodo’s docs). See multi-repo code review.
Qodo Leaves Linting to the Linter
Qodo’s findings are advisory, and your branch rules decide what merges. Keep ESLint, typescript-eslint and tsc in CI. For a wider comparison, see the best AI code review tools for GitHub monorepos.
Qodo Example: The API Field That Changed Shape
Context: an organization like a travel booking company with about 90 engineers is running a TypeScript web app and a Node.js API in separate repositories that share a types package.
Problem: an AI coding agent changed the API to return price as an object with an amount and currency instead of a number. The API’s tests passed, but the web app still treated price as a number in two places that used any.
How Qodo helped: with the two repositories linked, Qodo raised a Cross-repo finding on the API PR, pointing to the web app code that read price as a number.
Outcome: the break showed up on the PR that caused it, before merge, instead of after both apps shipped.
Ways to Review JavaScript and TypeScript Code
| Approach | What it catches | Limit | Best for |
|---|---|---|---|
| ESLint and typescript-eslint | Known bug patterns and style issues | Can’t judge behavior or intent | Every commit |
| TypeScript compiler | Type mismatches across the project | Blind to any and unsafe casts | Every build |
| Human code review | Design, behavior and intent | Slow at high PR volume | High-risk changes |
| The coding agent checking itself | Obvious issues in its own diff | Shares its own blind spots | Quick loops while coding |
| Qodo | Logic, rule and cross-repo findings with full codebase context | Advisory findings, with your branch rules as the gate; rule enforcement and cross-repo review are Beta | Enterprise teams that need team rules and cross-repo checks on every AI-written PR |
Qodo features in this table were checked against Qodo’s documentation as of October 28, 2026.
FAQ
Choose Qodo to review JavaScript and TypeScript pull requests with full codebase context and your team’s own rules. Most teams pair an AI reviewer with ESLint and the TypeScript compiler, so the linter handles known patterns and the reviewer handles behavior.
ESLint is the most widely used JavaScript linter. Teams using TypeScript add typescript-eslint for type-aware rules, and some use a quicker all-in-one tool for linting and formatting.
typescript-eslint lets ESLint read TypeScript code and adds rules that use type information, such as flagging promises that are never awaited.
TypeScript 7.0 doesn’t have a compiler API yet, so typescript-eslint and similar tools run alongside a TypeScript 6 package for now. Projects can use TypeScript 7 for builds and keep type-aware linting working.
A JavaScript code reviewer should check types, async code, null handling, security around user input, new dependencies and framework rules such as React hooks. Linters cover style and known patterns, so reviewers can focus on behavior.