Creating a TypeScript NPM Package

.gitignore

node_modules
build
dist
docs

api-extractor.json

{
  "projectFolder": ".",
  "mainEntryPointFilePath": "<projectFolder>/build/index.d.ts",
  "bundledPackages": [],
  "compiler": {
    "tsconfigFilePath": "<projectFolder>/tsconfig.json",
    "overrideTsconfig": {
      "compilerOptions": {
        "outDir": "build"
      }
    }
  },
  "dtsRollup": {
    "enabled": true,
    "untrimmedFilePath": "<projectFolder>/dist/index.d.ts"
  },
  "apiReport": {
    "enabled": false
  },
  "docModel": {
    "enabled": false
  },
  "tsdocMetadata": {
    "enabled": false
  },
  "messages": {
    "compilerMessageReporting": {
      "default": {
        "logLevel": "none"
      }
    },
    "extractorMessageReporting": {
      "default": {
        "logLevel": "none"
      }
    },
    "tsdocMessageReporting": {
      "default": {
        "logLevel": "none"
      }
    }
  }
}

package.json

{
  "name": "my-lib",
  "version": "1.0.0",
  "description": "Really awesome thing this does",
  "author": "Me <me@email.com> (https://www.website.com)",
  "homepage": "https://github.com/<username>/my-lib",
  "keywords": [
    "something",
    "awesome"
  ],
  "main": "dist/my-lib.cjs.js",
  "module": "dist/my-lib.esm.js",
  "browser": "dist/my-lib.umd.js",
  "files": [
    "dist"
  ],
  "scripts": {
    "dev": "rollup -c -w",
    "build": "rollup -c",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "dependencies": {
    "@rollup/plugin-commonjs": "^19.0.0",
    "@rollup/plugin-node-resolve": "^13.0.0",
    "@rollup/plugin-typescript": "^8.2.1",
    "eslint": "^7.26.0",
    "rollup": "^2.47.0",
    "ts-node": "^9.1.1",
    "tslib": "^2.2.0",
    "typescript": "^4.2.4"
  }
}

rollup.config.js

import resolve from "@rollup/plugin-node-resolve";
import commonjs from "@rollup/plugin-commonjs";
import typescript from "@rollup/plugin-typescript";
import pkg from "./package.json";

export default [
  // browser-friendly UMD build
  {
    input: "src/index.ts",
    output: {
      name: "myLib",
      file: pkg.browser,
      format: "umd",
    },
    plugins: [
      resolve(),
      commonjs(),
      typescript({ tsconfig: "./tsconfig.json" }),
    ],
  },

  // CommonJS (for Node) and ES module (for bundlers) build.
  // (We could have three entries in the configuration array
  // instead of two, but it's quicker to generate multiple
  // builds from a single configuration where possible, using
  // an array for the `output` option, where we can specify
  // `file` and `format` for each target)
  {
    input: "src/index.ts",
    output: [
      { file: pkg.main, format: "cjs" },
      { file: pkg.module, format: "es" },
    ],
    plugins: [typescript({ tsconfig: "./tsconfig.json" })],
  },
];

tsconfig.json

{
  "compilerOptions": {
    "target": "es6",
    "module": "esnext",
    "moduleResolution": "node",
    "strict": true,
    "esModuleInterop": true
  }
}