Detections

See which files, language features, module formats, and runtime APIs affect the minimum.

Runtime Checker discovers .js, .jsx, .mjs, .cjs, .ts, .tsx, .mts, and .cts files below the selected directory. It ignores .git, node_modules, dist, build, coverage, and target directories encountered inside that root.

Runtime APIs

The runtime databases map global APIs, namespaced methods, and selected owner-bound members to their first supported versions. Examples include:

  • Web APIs such as fetch, structuredClone, and Temporal.
  • Node APIs such as fs.cp, sqlite.DatabaseSync, and Symbol.asyncDispose.
  • Members whose compatibility depends on the owning object rather than only the property name.

The Oxc analyzer uses syntax and semantic context to avoid treating an unrelated local method named run, map, or columns as a runtime API.

JavaScript syntax

Syntax detections cover constructs whose parser support sets a minimum version, including optional chaining, nullish coalescing, logical assignment, await using, classes, modules, and many ordinary expressions and statements.

const name = account?.profile?.name ?? "Anonymous";

Each runtime receives the version associated with that syntax feature. The report's final minimum is the highest required version among all detections for that runtime.

Module format and native TypeScript

Runtime Checker identifies ESM, CommonJS, IIFE, and UMD patterns, plus native TypeScript type stripping when TypeScript source is passed directly to a runtime. This matters when scanning published source or scripts that are not transpiled before execution.

Grouped output separates APIs, syntax, module format, and native TypeScript entries. It collapses a shorter feature prefix when the same source location has a more specific detection, keeping the report focused on the strongest evidence.

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