How to stop execution of a node.js script?

Question

Say I've got this script:

var thisIsTrue = false;  exports.test = function(request,response){      if(thisIsTrue){         response.send('All is good!');     }else{         response.send('ERROR! ERROR!');         // Stop script execution here.     }      console.log('I do not want this to happen if there is an error.');  } 

And as you can see, I'd like to stop the script from executing any downstream functions if there's an error.

I've managed to achieve this by adding return; after the error response is sent:

var thisIsTrue = false;  exports.test = function(request,response){      if(thisIsTrue){         response.send('All is good!');     }else{         response.send('ERROR! ERROR!');         return;     }      console.log('I do not want this to happen if there is an error.');  } 

But is that the 'correct' way to do things?

Alternatives

I've also seen examples that use process.exit(); and process.exit(1);, but that gives me a 502 Bad Gateway error (I assume because it kills node?).

And callback();, which just gave me an 'undefined' error.

What is the 'correct' way to stop a node.js script at any given point and prevent any downstream functions from executing?

Answer 1

Using a return is the correct way to stop a function executing. You are correct in that process.exit() would kill the whole node process, rather than just stopping that individual function. Even if you are using a callback function, you'd want to return it to stop the function execution.

ASIDE: The standard callback is a function where the first argument is an error, or null if there was no error, so if you were using a callback the above would look like:

var thisIsTrue = false;  exports.test = function(request, response, cb){      if (thisIsTrue) {         response.send('All is good!');         cb(null, response)     } else {         response.send('ERROR! ERROR!');         return cb("THIS ISN'T TRUE!");     }      console.log('I do not want this to happen. If there is an error.');  } 

Answer 2

You should use return, which will help you respond to what happened. Here's a bit cleaner version, basically first validate whatever you want to validate, rather than encapsulating everything in if{}else{} statements

exports.test = function(request, response, cb){      if (!thisIsTrue) {         response.send('ERROR! ERROR!');         return cb("THIS ISN'T TRUE!");     }      response.send('All is good!');     cb(null, response)      console.log('I do not want this to happen. If there is an error.');  } 

Another way would be to use throw

exports.test = function(request, response, cb){      if (!thisIsTrue) {         response.send('ERROR! ERROR!');         cb("THIS ISN'T TRUE!");         throw 'This isn\'t true, perhaps it should';     }      response.send('All is good!');     cb(null, response)      console.log('I do not want this to happen. If there is an error.');  } 

Finally, examples that would stop entire app from further execution:

a) Throw an error, which will also help you debug the app (wouldn't completely stop the app, if the test() function was wrapper in try{}catch(e){}):

throw new Error('Something went wrong')

b) Stop script execution (works with Node.js):

process.exit()