Writing error handlers

To register custom error handlers in Koa, we simply need to define middleware with a try... catch statement to capture the errors, then send responses back to the client. This should be done at the top of the stack.

We can define error handlers based on various requirements to handle different types of errors for different types of clients. These error handlers can be used independently or combined, depending on the needs of the application. Let's define a set of error handlers and register them in our application:

const jsonErrorHandler = async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    const isJson = ctx.get('Accept') === 'application/json';
    if (isJson) {
      ctx.body = {
        error: 'An error just occurred'
      }
    } else {
      throw err;
    } 
  }
}

app.use(jsonErrorHandler);

The first error...