nodejs throw error what happens next code example

Example 1: node js throw error

FactoryController.prototype.create = function (callback) {
    //The throw is working, and the exception is returned.
    throw new Error('An error occurred'); //outside callback 
    try {
        this.check(function (check_result) {
            callback(check_result);
        });
    } catch (ex) {
        throw new Error(ex.toString());
    }
}

FactoryController.prototype.create = function (callback) {
    try {
        this.check(function (check_result) {
            //The throw is not working on this case to return the exception to the caller(parent)
            throw new Error('An error occurred'); //inside callback 
        });
    } catch (ex) {
        throw new Error(ex.toString());
    }
}

Example 2: error handling in call back function in nodejs

fs.readFile('/foo.txt', function(err, data) {
  // TODO: Error Handling Still Needed!
  console.log(data);
});