Thinking about fixing

A large part of a software developers job is to find problems. To find problems in existing applications and to minimize problems in applications.

This project is a broken Express application that you should fix to help you to think about fixing errors in your application. Because errors will be there for sure. How you interact and use them is crucial in your programming career.

Background

In this session we will look at tips, tricks and techniques for tracking down problems in our applications.

We will look at:

• How to track down errors
• Analyzing stack traces
• Isolating an issue
• Debugging tools

How to track down errors:

• Understanding the big picture
• What areas in the application are error prone
• What clues do we have?
• How to read error messages

Analyzing stack traces:

• Which code is yours?
• At which line is the error?
• Why could things go wrong at that line?
• Silent failure?

Isolating an issue:

• Remove code - check if it still fails
• Put code back until the error happens again
• Look at lines before & after the problem

Debugging tools

• Chrome developer tools - break points
• print things to the console.
• break problem down into components
• use log files - with various log levels

#Setup

Create a database

CREATE DATABASE debugging_tips;
CREATE USER debugger@localhost IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON debugging_tips.* TO debugger@localhost;
FLUSH PRIVILEGES;

Create tables

create table issues (
  id int not null auto_increment,
  heading char(100) not null,
  description text,
  primary key(id)
);

Install the dependencies

Using: npm install

Tools for break points

Node Inspector

Using MS Visual Code