@digibear/middleware

This is a middleware engine written in typescript that I've used on a couple of projects now. I've decided to turn it into it's own module for future reuse.

Installation

yarn add @udigibear/middleware

Usage

When you call the pipline function and assign it to a variable, you are able to pass a coma seperated list of middleware functions to add to the middleware queue.

import { pipeline } from "@digibear/middleware";

interface Context {
    [key: string]: any
}

const engine = pipeline<Context>((ctx, next) => {
    ctx.foobar="baz";
    next();
})

Not all middleware has to be added when the factory function is first invoked. Instead, you can assign middldeware to the system later with the use method.

engine.use(async (ctx, next) => {
  await new promise(res => setTimeout(() = res, 2000));
  ctx.another = 123;
  next();
});

Then when we're ready to run the middleware engine, we'll create it's it's initial context, and then pass that context to the engine for processing.

(async () => {
  const context: Context = {};
  await engine.exec(context);
  console.log(context);
})();

// => { foobar: "baz", another: 123 }

Errors

If an error happens in your middleware pipeline, you can assign an error handling middleware at the end of the queue.

engine.use((ctx, next) => {
  fs.readFile(ctx.path, {}, (err, file) => {
    if(err) next(err)
    
    // .. Do something
    
    next();
  })
})


// .. More middleware ...

engine.use((cyx, next, error) => {
 if (error) console.error(error.message);
})

Development

yarn -Dev install

Testing

yarn test

License

MIT