How do you handle JavaScript errors?

#discuss

Hi. I how do you handle JavaScript errors?

I wrote a sample function like this;

Function

let tried = function(callback) {
    let err = null

    let errorObject = {}

    try {
        callback()
    } catch(ex) {
        err = ex
    }

    return {
        catch: function(data, cb) {
            if(err) {
                if(cb) {
                    switch(err.name) {
                        case 'EvalError':
                            if(data == 'EvalError') cb(err)
                            break;
                        case 'InternalError':
                            if(data == 'InternalError') cb(err)
                            break;
                        case 'RangeError':
                            if(data == 'RangeError') cb(err)
                            break;
                        case 'ReferenceError':
                            if(data == 'ReferenceError') cb(err)
                            break;
                        case 'SyntaxError':
                            if(data == 'SyntaxError') cb(err)
                            break;
                        case 'TypeError':
                            if(data == 'TypeError') cb(err)
                            break;
                        case 'URIError':
                            if(data == 'URIError') cb(err)
                            break;
                        case 'Error':
                            if(data == 'default') cb(err)
                            break;
                        default:
                            cb(err)
                            break;
                    }
                }
            }
            return this
        }
    }
}

Usage

tried(() => {
    thisMethodNotExist()    
}).catch('EvalError', (err) => {
    console.log('Eval error')
}).catch('InternalError', (err) => {
    console.log('Internal error')
}).catch('RangeError', (err) => {
    console.log('Range error')
}).catch('ReferenceError', (err) => {
    console.log('Referans error') // this scope will run.
}).catch('SyntaxError', (err) => {
    console.log('Syntax error')
}).catch('TypeError', (err) => {
    console.log('Tip error')
}).catch('URIError', (err) => {
    console.log('URI error')
}).catch('Error', (err) => {
    console.log('Generic Error')
}).catch('default', (err) => {
    console.log('Custom Error')
})

This function helped me many times. Do you have any method like this? Or what is your approach to catching error handling?

Top comments (5)

Basti Ortiz • Dec 26 '18 • Edited

Just saying, there's no need to catch all the types of errors in your script. Only catch those you expect to be thrown. For example, there's no reason to catch an EvalError if window.eval is not used in your code.

But to answer your question, it seems like your error handling function does the same thing over and over again; that is to do something about a specific error. For a more straightforward method of catching errors, you can simply use the instanceof operator in the catch block.

try {
  // Insert some erroneous code here...
} catch (err) {
  if (err instanceof EvalError) { /*...*/ }
  else if (err instanceof InternalError) { /*...*/ }
  else if (err instanceof RangeError) { /*...*/ }
  else if (err instanceof ReferenceError) { /*...*/ }
  else if (err instanceof SyntaxError) { /*...*/ }
  else if (err instanceof TypeError) { /*...*/ }
  else if (err instanceof URIError) { /*...*/ }
  else if (err instanceof Error) { /*Generic error...*/ }
  else { /*Custom error...*/ }
}

Or if you simply want to log the type of error you caught, you can use the Error#name instance property.

try {
  // Some erroneous code here...
} catch (err) {
  console.log(`Oh, no! A ${err.name} was caught!`);
}

Itachi Uchiha • Dec 26 '18

Hi. Thanks for your answer. Yes, I realized that I can use that like how you coded.

I coded this function because of errors I didn't know. In this example, I wanted to catch specific errors.

But your code looks more professional than me.

Is there any function to catch global errors in the JavaScript?

Basti Ortiz • Dec 26 '18

I'd say the try-catch block is good enough for most use cases.

If you're interested, MDN has a list of all the types of errors in JavaScript. You can start diving there for error handling. If you're already familiar with other programming languages, it shouldn't be too different from what you already know.