downlevel-dts

What is downlevel-dts?

The downlevel-dts npm package is used to downlevel TypeScript declaration files (.d.ts) to an older version of TypeScript. This is useful for library authors who want to support older versions of TypeScript without maintaining multiple versions of their codebase.

What are downlevel-dts's main functionalities?

Downlevel TypeScript Declarations

This feature allows you to downlevel TypeScript declaration files to a specified TypeScript version. In this example, the input .d.ts file is downleveled to TypeScript version 3.7 and written to the output file.

const downlevelDts = require('downlevel-dts');
const fs = require('fs');

const inputFilePath = 'path/to/input.d.ts';
const outputFilePath = 'path/to/output.d.ts';

const inputDts = fs.readFileSync(inputFilePath, 'utf8');
const outputDts = downlevelDts(inputDts, '3.7');

fs.writeFileSync(outputFilePath, outputDts);

Other packages similar to downlevel-dts

typescript

The TypeScript package itself can be used to generate declaration files, but it does not provide functionality to downlevel existing declaration files. It is more focused on compiling TypeScript code to JavaScript and generating .d.ts files from TypeScript source code.

api-extractor

API Extractor is a tool for managing and analyzing the public API surface of a TypeScript library. While it provides features for generating and validating .d.ts files, it does not specifically focus on downleveling them to older TypeScript versions.

dts-bundle-generator

dts-bundle-generator is a tool for generating a single .d.ts file from a TypeScript project. It focuses on bundling multiple declaration files into one, rather than downleveling existing declaration files.

README

Usage

1. $ npm install downlevel-dts
2. $ npx downlevel-dts . ts3.4
3. To your package.json, add

"typesVersions": {
  "<=3.4.0-0": { "*": ["ts3.4/*"] }
}

1. $ cp tsconfig.json ts3.4/tsconfig.json

These instructions are modified and simplified from the Definitely Typed.