How to post ExpressJS errors to your Discord Channel

Step 1:

Create a Discord Channel in your Discord server.

Step 2:

Under Integrations, create a new Webhook that has the new channel in its settings. Download the Webhook URL.

Step 3:

Find your ExpressJS application error handler in app.js that looks like below:

const errorHandler = function(err, req, res ,next) {
    // Error handler

}

Step 4:

Install the node-fetch package:

npm install node-fetch —save

Step 5:

Call Discord with your error and request details making a POST request with node-fetch, and filling in the content: field of an object, then converting it to JSON string. The content can only be text. Optionally you may create an ascii table using the ascii-table3 package. Check out the sample code below.

const errorDiscordData = function(err, req, res, next) {

    let table = errorToTable(err, req, res, next);

    let data = "\`\`\`" + table.toString() + "\`\`\`"

    let domainPath = null;

    domainPath = req.hostname;

    if (process.env.NODE_ENV == "production") {

      domainPath = "https://" + domainPath;

    } else {

      domainPath = "http://" + domainPath + ":8081";

    }

    if (req.path != "/")

      domainPath += req.path;

    // Discord doesn't visit the link when link posted in chat as wrapped in <>

    // This helps, because without below fix, for every 404 error discord goes and triggers 3 others of the same.

    domainPath = "<" + domainPath + ">"

    return data + domainPath

}

const errorToTable = function(err, req, res, next) {

  let username = req.user && req.user.firstname && req.user.lastname ? req.user.firstname + " " + req.user.lastname : null;

  let userhandle = null;

  // If name exists, use name + email, else just email, if no user use null.

  if (req.user) {

    if (username) {

      userhandle = username + " " + req.user.email

    } else {

      userhandle = req.user.email

    }

  } else {

    userhandle = null;

  }

  let table = 

    new asciitable.AsciiTable3()

    .setHeading('app', 'user', 'method', 'error')

    .setAlignCenter(3)

    .addRowMatrix([

        [req.thisApp ? req.thisApp.id : null,

         userhandle,

         req.method,

         err.message

        ],

    ]);

  // set compact style

  table.setStyle('compact');

  return table;

}

// error handler

app.use(function(err, req, res, next) {

  // set locals, only providing error in development

  res.locals.message = err.message;

  res.locals.error = req.app.get('env') === 'development' ? err : {};

  let headers = new fetch.Headers();

  headers.set('Content-Type', 'application/json');

  return fetch(discord_url, {

    method: "post",

    body: JSON.stringify({ content: errorDiscordData(err, req, res, next) }),

    headers: headers

  }).then(response => {

      //console.log("Discord response:", result)

      // Only share call stack in development

      if (process.env.NODE_ENV == "development") {

         // console.error(err);

      }

      // Handle passport login error:

      if (handleSeparateAppLogin(err, req, res, next)) {

        return;

      }

      // render the error page

      res.status(err.status || 500);

      res.render('default/marketing/error', { cache: directive, error: err });   

  })

});

Using this code, you can now post all your server errors to a Discord channel, analyze frequently occurring errors in real-time and fix them!