A nice lil' JS error handling pattern

errorHandling.js

function thisThrows() {
    throw new Error('Original error')
}

function thisAddsContextAndThrowsAgain() {
    try {
        thisThrows()
    } catch(err) {
        err.message = 'More info: ' + err.message
        err.statusCode = 404
        throw err // note that we don't `throw new Error(err)` or we lose some stack info
    }
}

function main() {
    try {
        thisAddsContextAndThrowsAgain()    
    } catch(err) {
        console.log(err.statusCode) // prints 404
        console.error(err) // prints the message with stack below
        /*
        customError.js:20 Error: More info: Original error
          at thisThrows (VM200 customError.js:2)
          at thisAddsContextAndThrowsAgain (VM200 customError.js:7)
          at main (VM200 customError.js:17)
          at VM200 customError.js:24
        */
    }
}

main()

Here's a little pattern I like for modifying errors in JS. Modifying the err.message will add info anywhere it's toString()'d (like console.log), and re-throwing the error will add stack trace info at each throw location. Also, you can add your own custom keys to the err object. Though even with typescript, there's no good way to gain type safety on thrown errors, so do this carefully.