Express-Echo-Server.js

/*
  In this Express exercise, your task is to create an app that responds to GET and POST requests on the / route.
  The responses will echo a message string from the request.

GET /
This route will read the message parameter and send a JSON response containing the echoed message value. The response should have a 200 status.

An example query string is ?message=hello which would be echoed as {"message": "hello"}. An empty string, ?message=, is valid and should be echoed normally.

Respond with a 422 status when no query parameter message exists, or if the message type is other than a string.
The Content-Type header should be set to text/plain rather than application/json in this case.

POST /
This route will parse the request body as JSON and echo a response containing the value from the "message" key of the request.
The JSON response is in the same format as the GET above: {"message": "some message"}. Set a 200 status on the response to indicate that the request was OK.
An empty string ("message": "") is valid and should be echoed.

Respond with a 422 status when no "message" key exists, or if the message type is other than a string.
The Content-Type header should be set to text/plain rather than application/json in this case.

All JSON sent to the POST route will be well-formed.

For either method, a request is still valid if additional parameters or keys are present in the query or JSON body. You can ignore them and echo message as normal.

Notes
Please use the variable name app to implement your server.
Don't use app.listen() to start the Express server; the test suite will invoke the route handlers directly on the app object.

Your solution file is automatically included with the test suite, so no export is necessary.

Test input strings consist of alphanumeric characters and spaces.

If you're not familiar with the Express concepts needed to complete this kata, feel free to reference the documentation and other resources as you build your solution.
*/

// Answer:

const express = require("express");
const app = express(); // be sure to use the variable `app`

app.use(express.json());

app.get('/', (req, res) => {
  let {message} = req.query;
  if(message === undefined || typeof message !== 'string') {
    res.contentType('text/plain').sendStatus(422);
  }
   
  res.status(200).json( {message} );
})

app.post('/', (req, res) => {
  let {message} = req.body
  if(message === undefined || typeof message !== 'string') {
    res.contentType('text/plain').sendStatus(422);
  } 
  res.status(200).json({message});
})