Node.js ESLint API Usage

Use this pattern when embedding linting in scripts, custom tooling, or release checks.

Minimal API flow

import { ESLint } from "eslint";
import typefest from "eslint-plugin-typefest";

const eslint = new ESLint({
  overrideConfig: {
    files: ["**/*.ts"],
    plugins: {
      typefest,
    },
    rules: {
      "typefest/prefer-type-fest-primitive": "error",
    },
  },
});

const fileResults = await eslint.lintFiles(["src/**/*.ts"]);

const textResults = await eslint.lintText(
  "type PrimitiveAlias = string | number | bigint | boolean | symbol | null | undefined;",
  { filePath: "virtual.ts" }
);

const allResults = [...fileResults, ...textResults];

await ESLint.outputFixes(allResults);

const formatter = await eslint.loadFormatter("stylish");
console.log(formatter.format(allResults));

API usage notes

• lintFiles(...) is best for repository scans.
• lintText(...) is useful for generated/virtual content.
• ESLint.outputFixes(...) writes autofix changes to disk for file-based results.
• loadFormatter(...) lets you switch output style per integration context.

Debugging API integrations

• Compare API output with CLI output for the same target files.
• Use --print-config with matching file paths to validate effective settings.
• Ensure API runtime uses the same Node version and dependency graph as CI.