Express-res-errors

Express-res-errors is a package for throwing errors inside express routes. It handles these error with a custom express middleware. The package is made to be used in Typescript but can potentially also be used in Javascript.

Features

• HTTPError

• Default Errors

• Custom Errors

Example

app.get("/myRoute", (req, res) => {
  throw new BadRequestError();
});

// After your routes
app.use(
  errorHandlerMiddleware({
    // Config
  })
);

Usage with async routes

app.get("/myRoute", async (req, res, next) => {
  next(
    new BadRequestError()
  );
});

Or install express-async-errors if you want to throw errors inside of async routes.

import "express-async-errors";

// ...

app.get("/myRoute", async (req, res) => {
  throw new BadRequestError();
});

HTTPError

Example:

app.get("/myRoute", (req, res) => {
  throw new HTTPError(500, {
    message: "My Custom JSON Body"
  });
});

Default Errors

Example:

app.get("/myRoute", (req, res) => {
  throw new InternalServerError();
});

This package includes all 400 and 500 status codes.

Custom Errors

You can create custom errors yourself. This is very useful if you want every error to return the same JSON structure.

class MyCustomError extends CustomError {
  statusCode = 400; // The status code the error should send

  constructor(public returnMessage: string) {
    super("Bad Request"); // Error message
    Object.setPrototypeOf(this, MyCustomError.prototype); // Required in order to let the custom error work
  }

  serializeErrors() {
    return [{
      message: this.returnMessage
    }]
  }
}

serializeErrors returns by default this typescript type: { message: string; field?: string }[]; The purpose of serializeErrors is that it converts variables, passed in by the constructor to this typescript type so that the JSON body with every error looks the same. Useful use case can be found here.

You can change the return type of serializeErrors. In this example, serializeErrors should return an object with key message that has a value that is a string.

class MyCustomError extends CustomError<{ message: string }> {
    // ...
}