NestedError

NestedError is an Error class useful for wrapping another Error to get a better stack trace associated with it.

This can be very helpful, especially when the original Error is created close to node's internal event loop.

Usage

First, install NestedError: npm install nested-error

Then make use of it like in this illustrative example:

var net = require('net');
var NestedError = require('nested-error');

// This function is our program:
function listen(callback) {
  // Connect to a nonexistent UNIX domain socket to
  // cause an error in the net module:
  var server = net.connect({ "path": "nonexistent" });

  server.on('error', function (err) {
    // Wrap the error message we get in a NestedError
    // to attach a stack trace that goes here
    callback(new NestedError(err));
  });
}


// This should give an error callback
listen(function (err) {
  if (err) {
    // Write out both stack traces for comparison:
    console.error(err.stack);
    console.error("\nCompare to inner exception:");
    console.error(err.innerException.stack);
    console.error("\nConclude that NestedError lets you debug easier :)");
  }
});

This program will output the stack traces for both the error object we got from node's net module and the NestedError we created. The NestedError gives a much better context to be able to debug the problem.