How to correctly raise errors in node.js

gistfile1.js

// example function that raises an error
function example (callback) {

    // correct approach
    return callback ( new Error('an error occurred') );

    // NO! BAD KITTY!
    return callback ('an error occurred');

} // some_function()


// call example function
example( function (err, result) {

    // if you passed an error object, this will give
    // you additional information about the error, i.e.
    // the stacktrace. If you only passed a string,
    // you would now only see that string.
    if (err) console.log(err);

});