Jsonnet for TypeScript and JavaScript

Jsonnet is a templating extension of JSON.

The design is influenced by several configuration languages internal to Google, and embodies years of experience configuring some of the world's most complex IT systems. Jsonnet is now used by many companies and projects.

For the tplfa-jsonnet package, Jsonnet is compiled from Go to WASM and wrapped with helper functions.

The letters "tplfa" stay for "Templating for API", a project to provide a unified interface to generative AI providers. tplfa-jsonnet is the foundation part of the larger project.

Installation

npm install tplfa-jsonnet

Usage

Load the library in Node.js:

import 'tplfa-jsonnet/wasm_exec.js';
import { Jsonnet, getJsonnet } from 'tplfa-jsonnet/jsonnet';
...

const jsonnetWasm = await fs.promises.readFile(
  require.resolve('tplfa-jsonnet/libjsonnet.wasm')
);
jsonnet = await getJsonnet(jsonnetWasm);

Load the library in the browser:

<script src="/js/wasm_exec.js"></script>
<script src="/js/jsonnet-web.js"></script>
<script>
const jsonnetPromise = (async () => {
  console.log('Loading libjsonnet: started');
  const jnWasm = fetch('/js/libjsonnet.wasm');
  const jn = await getJsonnet(jnWasm);
  console.log('Loading libjsonnet: done');
  return jn;
})();
</script>

The jsonnet object provides two functions:

• jsonnet_evaluate_snippet: Wrapper for the corresponding jsonnet library function
• evaluate: Simplified interface. Only code, its external variables, and library files

The function signature:

evaluate: (
  //
  // Jsonnet code
  //
  code: string,

  //
  // Optional variables.
  // The values should be stringified.
  // For use in the Jsonnet code:
  //
  //   std.extVar("<var name>")
  //   std.parseJson(std.extVar("<var name>"))
  //
  extrStrs?: Record<string, string>,

  //
  // Optional library code. For use in the Jsonnet code:
  //
  //   import "<file name>"
  //
  files?: Record<string, string>

  //
  // Output: serialized JSON. Use `JSON.parse` to deserialize.
  //
) => Promise<string>;

Full examples

See:

• Browser environment: https://github.com/olpa/templating-for-api/tree/master/in-action/web-jsonnet/
• Node.js environment: https://github.com/olpa/templating-for-api/tree/master/in-action/nodejs-jsonnet/

Compatibility note

For old node versions, you need to edit the file wasm_exec.js. After the line use strict add line globalThis.crypto ??= require('crypto');. Maybe more changes are needed: https://github.com/golang/go/issues/53128.

License, contact

MIT

Jsonnet: Apache license 2.0

Oleg Parashchenko [email protected]