Examples of express behavior for TypeErrors

type-errors.js

'use strict'

const express = require('express')
const request = require('request')

const configureRoute = handler => async (req, res, next) => {
	try {
		handler(req, res, next)
	} catch (error) {
		// we successfully caught an error
		res.send('Successfully caught the error')
	}
}

function handlerWithoutCallstack(data, next) {
	callbackStyleFunction({}, next)
}

function handlerWithCallstack(data, next) {
	request('http://google.com', () => {
		callbackStyleFunction({}, next)
	})
}

function callbackStyleFunction(data, next) {
	// TypeError because "missingProperty" is undefined"
	next(null, data.missingProperty.boom)
}

const app = express()

// this error is successfully caught because it is 
// in same callstack as the route handler
app.use('/no-callstack', configureRoute(handlerWithoutCallstack))

// this error is not successfully caught because it is 
// in a different callstack than the route handler
app.use('/callstack', configureRoute(handlerWithCallstack))

app.listen(3333, () => {
	console.log('server up...')
})