@kongyo2/similarity-ts
@kongyo2/similarity-ts is a free TypeScript-only analyzer for structurally comparing functions, types and classes across a repository.
What @kongyo2/similarity-ts is
@kongyo2/similarity-ts is a free TypeScript-only analyzer for structurally comparing functions, types and classes across a repository. The package provides a CLI and JavaScript library and requires Node.js 20 or newer. A quick start scans the current directory with npx @kongyo2/similarity-ts .. By default it checks .ts, .tsx, .mts and .cts files, using functions, types, classes and overlap modes. Equivalent coding styles such as arrow functions and declarations, .then() and await, and selected loop forms are normalized. Parameters, locals, inner functions and declaration names are alpha-renamed, while free identifiers remain significant. Behavior-changing forms such as map versus filter, async versus synchronous code, and ?? versus || stay distinct. Users can set thresholds, minimum sizes, extensions, exclusions and output format. Pretty or JSON reports are available, alongside --fail-on-duplicates for CI.
Good
- Free MIT-licensed package
- CLI and JavaScript library forms
- AST-based repository scanning
- Pretty, JSON and CI-failure outputs
- Normalizes several equivalent coding styles
Watch out
- Requires Node.js 20 or newer
- No IDE integration is listed
- Supports TypeScript file extensions by default
Who it suits
This suits TypeScript developers and teams seeking repository-level duplicate-code analysis. It also fits CI workflows and refactoring work assisted by AI coding tools.
Verdict
similarity-ts offers configurable structural similarity analysis for TypeScript repositories, with normalization that separates stylistic changes from behavioral differences. Its CLI, library entry point and CI option make it practical for automated duplicate detection.
The facts
Each one read from @kongyo2/similarity-ts's own pages, with the date it was checked.
What it does
- Accuracy benchmark
- The README reports that version 0.7.0 correctly labeled all 300 pairs in its stated benchmark corpus.checked 7 Oct 2026
- Analysis modes
- Its default modes are functions, types, classes, and overlap, and the README documents options to select modes and restrict scan scope.checked 5 Oct 2026
- Analysis targets
- It compares functions, types, and classes structurally.checked 7 Oct 2026
- Behavioral distinctions
- The README says behavior-changing differences such as `.map` versus `.filter` and `async` versus synchronous contracts retain distinct shapes.checked 7 Oct 2026
- CI use
- The CLI offers a `--fail-on-duplicates` option that exits non-zero when any pair is reported.checked 7 Oct 2026
- CLI controls
- The CLI supports selecting analysis modes, setting a similarity threshold, filtering file extensions, excluding patterns, and choosing pretty or JSON output.checked 7 Oct 2026
- Code style matching
- It canonicalizes documented style variants, including arrow functions versus declarations, `.then()` versus `await`, and several loop forms.checked 5 Oct 2026
- Exclusions
- A declaration can be excluded from the report with a `// similarity-ignore` comment on the preceding line.checked 5 Oct 2026
- Install and run
- The README’s quick start runs the analyzer with `npx @kongyo2/similarity-ts .`.checked 5 Oct 2026
- Intended workflow
- The README suggests using the command with an AI coding assistant to find duplicate code patterns and create a refactoring plan.checked 7 Oct 2026
- License
- The repository identifies its license as MIT.checked 7 Oct 2026
- Output and CI
- It supports pretty or JSON output and a `--fail-on-duplicates` option that exits nonzero when any pair is reported.checked 5 Oct 2026
- Package form and runtime
- The package metadata describes a CLI and library, exposes a command-line binary and JavaScript entry point, and specifies Node.js 20 or newer.checked 5 Oct 2026
- Package formats
- The package metadata exposes both a `similarity-ts` command-line executable and a JavaScript library entry point with TypeScript declarations.checked 7 Oct 2026
- Purpose
- The project describes itself as a TypeScript-only similarity analyzer for detecting semantic code similarities.checked 7 Oct 2026
- Rename handling
- It alpha-renames function parameters, locals, inner functions, and declaration names before comparison, while retaining free identifier names.checked 7 Oct 2026
- Runtime requirement
- The package metadata specifies Node.js version 20 or newer.checked 7 Oct 2026
- Style normalization
- The analyzer canonicalizes several equivalent coding forms, including function declarations and arrow functions, some loop rewrites, and structurally identical interfaces and type aliases.checked 7 Oct 2026
- Supported file extensions
- The default extensions it scans are `ts`, `tsx`, `mts`, and `cts`.checked 5 Oct 2026
- Threshold and size controls
- The similarity threshold defaults to 0.8, the minimum function length defaults to three lines, and a minimum AST-token size can replace the line gate.checked 5 Oct 2026
- Usage
- The README shows running it on the current directory with `npx @kongyo2/similarity-ts .`.checked 7 Oct 2026
The company
- Maker identity
- The repository is hosted under the GitHub account `kongyo2`; the opened project pages do not state a maker’s personal or company name, headquarters, or founding date.checked 5 Oct 2026
