bree/examples/typescript-esm/README.md

Working with TypeScript

This is the most basic bree example that shows a basic workflow for working with bree and typescript.

Using the root option

It is generally best to set the bree root option when using any tool that may be tranpiling your code. Generally it makes the most sense to set it to path.join(__dirname, 'jobs'). If you are compiling to ESModules, you should set it to path.join(path.dirname(fileURLToPath(import.meta.url)), 'jobs') as the global __dirname variable will be unavailable.

Using TS Node

TS Node is a project that uses hooks to compile typescript on the fly for fast and convenient TypeScript development. In order to use bree successfully with TS Node and to be able to write your jobs in TypeScript - one needs to run it in such a way that allows TS Node to transpile child process and worker scripts on the fly.

We do this by implementing a dev script in our package.json as is outlined in the TS Node docs..

"dev": "TS_NODE=true NODE_OPTIONS=\"-r ts-node/register\" node ."

We further add a TS_NODE env var, as when in a TS Node environment, we need to append ts file extensions to our worker paths instead of the default JS. However, when we compile the code for production with the TypeScript compiler (running tsc), we need to keep the default js extensions on our worker paths.

Compiling to ESModules

To compile to ESModules first set "type": "module" in your package.json. Ensure your compiler options are set to compile to ESModules output. After that, we need to change our dev script in our package.json so TS Node properly compiles workers to ESModules as well.

"dev": "TS_NODE=true NODE_OPTIONS=\"--loader ts-node/esm\" node ."

In our tsconfig.json we need to ensure that our moduleResolution is set to node and that module is set to an option that will give the output as esmodule syntax as seen in this example.