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Choose a JavaScript runtime by naming the specific language features and APIs your project needs, checking the minimum version that supports them, and testing your code and dependencies on that exact version. “Modern language features” is not one compatibility setting: JavaScript syntax, TypeScript syntax, and runtime APIs have different requirements.
First separate JavaScript syntax, TypeScript, and runtime APIs
JavaScript syntax support depends on the runtime’s embedded engine and its version. TypeScript adds a separate question: does the runtime merely remove type annotations, transform TypeScript constructs into JavaScript, or require an external compiler? None of those actions necessarily type-checks your program.
Runtime APIs are another category. A syntax feature may be part of the ECMAScript language, while APIs such as filesystem or networking functions are supplied by the host runtime. Ecma International describes the relationship this way: “The ECMAScript language is defined in terms of a host that provides the runtime environment for the execution of scripts.” See ECMA-419, third edition.
Start by identifying the actual feature, API, or TypeScript construct in your code. Then determine its supported runtime version and test it against the version you plan to deploy. General labels such as “modern” do not establish compatibility.
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Compare the TypeScript workflow and compatibility you need
| Runtime | TypeScript workflow | Compatibility checks | Consider it when |
|---|---|---|---|
| Node.js | Built-in type stripping is stable in the documented releases v24.12.0 and v25.2.0 onward. It removes erasable types but does not type-check. Constructs requiring generated JavaScript—including value enums, namespaces with runtime code, parameter properties, and import aliases—are rejected. Built-in stripping ignores tsconfig.json, so its transformation and path-resolution settings are not applied. |
Check the exact Node.js version and whether your source uses only erasable TypeScript syntax. Add a separate checker or compiler if you need type checking or transformations. See Node.js TypeScript documentation. | You need the Node.js ecosystem and your code fits its built-in syntax support, or you already use a compiler/transpiler workflow. |
| Deno | deno run strips TypeScript types and passes JavaScript to V8 without checking types. Use deno check or deno run --check to invoke the TypeScript checker. Deno also documents integrated linting and formatting. |
Check the specific Node APIs and packages you depend on. Deno’s compatibility guide describes support for most Node built-ins, npm packages, Node globals, package.json, CommonJS, optional node_modules layouts, and Node-API native addons under stated conditions; some APIs are partial and some packages expect a local node_modules layout. See Node and npm compatibility and modules and dependency management. |
You value integrated TypeScript tools and Deno’s workflow, and your required APIs and dependencies work in the project’s actual setup. |
| Bun | Bun says it supports TypeScript and JSX without configuration and transpiles files on the fly. That execution workflow does not by itself establish that type checking is performed. | Bun’s regularly updated Node compatibility page reflects compatibility with Node.js v26 and records status and caveats by module. Check entries for your own APIs and packages. See Bun Node.js compatibility. | You want integrated execution and transpilation, and your dependencies pass tests under the Bun version you intend to deploy. See Bun runtime documentation. |
These are workflow distinctions, not a project-specific test result or a universal ranking. Deno states that over 75% of Node.js’s own test suite passes in Deno 2.8; that figure applies to that suite and version, not to 75% of all Node packages or APIs. Bun’s compatibility page reports module-level test results, including 99% for node:dgram, 95% for node:events, and 98% for node:fs; these are results for the named module test suites, not an overall compatibility score.
Use this decision process for your project
- Inventory the code you must run. List the JavaScript syntax, TypeScript syntax, JSX or TSX, and any TypeScript constructs that require generated runtime code. Establish the minimum runtime version for each requirement.
- Choose where type checking belongs. Decide whether checking must happen in the execution command or in a separate build or CI stage. Node.js built-in stripping does not check types; Deno documents separate checking commands; Bun documents on-the-fly transpilation.
- Check dependencies and module assumptions. Verify ESM and CommonJS behavior, Node built-in APIs, npm packages, native addons, module resolution, and whether packages expect a local
node_moduleslayout. - Check the deployment environment. Confirm that the target platform offers the runtime versions you need, and account for its permissions and operating environment.
- Test the actual candidate versions. Run the project’s tests and deployment build with each runtime version under consideration. Keep your test results distinct from vendor documentation claims.
- Measure performance only if it matters to the choice. If startup time, throughput, or memory are requirements, compare candidates using the same workload on the target environment. No universal performance ranking follows from language-feature support.
How to decide between close candidates
Compare candidates against your requirements rather than counting supported features in the abstract. A useful comparison records the version floor and syntax coverage, the TypeScript transformation and checking workflow, package and API compatibility, module behavior, and deployment constraints. Add measured performance only when you have tested the same workload under comparable conditions.
Compatibility documentation is vendor-maintained and can change with releases. Recheck the relevant documentation when selecting a runtime version, and treat a broad compatibility statement or test-suite percentage as a starting point—not proof that your application works.
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