Exceptions thrown in asynchronous javascript not caught

Question

Basically, why isn\'t this exception caught?

var http = require(\'http\'),
    options = {
      host: \'www.crash-boom-bang-please.com\',
      port: 80,
               


        

Answer 1

When you are throwing the error the try {} block has been long left, as the callback is invoked asynchronously outside of the try/catch. So you cannot catch it.

Do whatever you want to do in case of an error inside the error callback function.

Answer 2

As of node version 0.8 you can constrain exceptions to domains. You can constrain exceptions to a certain domain and catch them at that scope

If you're interested, I've written a small function that catches asynchronous exceptions here: Javascript Asynchronous Exception Handling with node.js. I'd love some feedback This will let you perform the following:

var http = require('http'),
    options = {
      host: 'www.crash-boom-bang-please.com',
      port: 80,
      method: 'GET'
    };

atry(function(){
  var req = http.request(options, function(res) {
    res.setEncoding('utf8');
    res.on('data', function (chunk) {
      console.log('BODY: ' + chunk);
    });
  });

  req.on('error', function(e) {
    throw new Error("Oh noes");
  });
  req.end();
}).catch(function(_error) {
  console.log("Caught the error");
});

Answer 3

Javascript doesn't have just function scope, try-catch also is block scoped. That is the reason.