@typeonly/loader

TypeOnly aims to be the pure typing part of TypeScript. The TypeOnly parser generates a .to.json file, which is a bundle that contains metadata extracted from .d.ts typing files. Then, this package provides an API to read these RTO files. It brings typing metadata at runtime.

Tutorial: Load typing definitions at runtime

At first, it is necessary to follow the tutorial of TypeOnly in order to generate a .to.json file based on your TypeScript definitions. After this step, you have the following file: dist/types.to.json.

Now, add @typeonly/loader to the project:

npm install @typeonly/loader

Create a file src/main.js with the following content:

// src/main.js
const { loadModules, literals } = require("@typeonly/loader");

const modules = loadModules({
  bundle: require(`./types.to.json`)
});

const { ColorName } = modules["./drawing"].namedTypes;
console.log("Color names:", literals(ColorName, "string"));

If you write this code in a TypeScript source file, simply replace the require syntax with a standard import.

We can execute our program:

$ node src/main.js
Color names: [ 'red', 'green', 'blue' ]

Yes, it’s as easy as it seems: the list of color names is now available at runtime.

Notice: The TypeOnly parser is used at build time. At runtime, our code only use @typeonly/loader which is a lightweight wrapper for .to.json files.

Contribute

With VS Code, our recommanded plugin is:

• TSLint from Microsoft (ms-vscode.vscode-typescript-tslint-plugin)