Gaurav Sehrawat

Tech Consultant(Javascript/Python)

Full Stack Developer

Twitter: root3d

Github: igauravsehrawat

What is debugging?

Debugging Node.js

Code for the talk is available in payroll-system repo on Github

Console.log be like

Node.js Debugger

From the start

node inspect yourScript.js

In the middle of script

Insert debugger;

Shortcuts

• continue
• next
• pause
• restart
• run
• kill

    from IPython.display import IFrame    
    display(IFrame("http://nodejs.org/en/docs/guides/debugging-getting-started/", width=900, height=650))

Demo

Real world

Inspecting Running Server in Devtools

node --inspect script/server

Flags

• --inspect-brk
• --inspect=<port>

Nice Inspector Manager

https://chrome.google.com/webstore/detail/nodejs-v8-inspector-manag/gnhhdgbaldcilmgcpfddgdbkhjohddkj?hl=en

Recent tool by GoogleChromeLabs

NDB

With Additional Features Exclusively For Node.js

• Child processes are detected and attached to
• Place breakpoints before the modules are required
• Edit files in UI. Devtools will save changes to the disk
• ndb blackboxes all scripts outside current working directory

No more console.log

All that is fine

But never run debugger in production mode

Interesting bug exposed via debug mode:

Facebook Debug Bug

Production level debugging

• Use the npm debug packagage

• Use a logger (Winston, log4js, bunyan)

Debug package

• Lot of existing packages use debug

For e.g: Express, socket.io, mongoose, many more.

Debug database

mongoose.set('debug', true)

Winston package

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.json(),
  transports: [
    //
    // - Write to all logs with level `info` and below to `combined.log` 
    // - Write all logs error (and below) to `error.log`.
    //
    new winston.transports.File({ filename: 'error.log', level: 'error' }),
    new winston.transports.File({ filename: 'combined.log' })
  ]
});

//
// If we're not in production then log to the `console` with the format:
// `${info.level}: ${info.message} JSON.stringify({ ...rest }) `
// 
if (process.env.NODE_ENV !== 'production') {
  logger.add(new winston.transports.Console({
    format: winston.format.simple()
  }));
}

logger.log('silly', "127.0.0.1 - there's no place like home");
logger.log('debug', "127.0.0.1 - there's no place like home");
logger.log('verbose', "127.0.0.1 - there's no place like home");
logger.log('info', "127.0.0.1 - there's no place like home");
logger.log('warn', "127.0.0.1 - there's no place like home");
logger.log('error', "127.0.0.1 - there's no place like home");
logger.info("127.0.0.1 - there's no place like home");
logger.warn("127.0.0.1 - there's no place like home");
logger.error("127.0.0.1 - there's no place like home");

Sentry

If you like to get an alarm in the middle of night

https://docs.sentry.io/learn/configuration/?platform=javascript

Keep monitoring them using Slack Plugin

https://sentry.io/integrations/slack/

Demo!!

Other strategies

Typescript?

Elm?

Flow?

Take no suprises!!

from IPython.display import IFrame    
display(IFrame("https://www.typescriptlang.org/", width=900, height=650))

from IPython.display import IFrame    
display(IFrame("https://elm-lang.org/", width=900, height=650))

from IPython.display import IFrame    
display(IFrame("https://flow.org/", width=900, height=650))

TDD

Test Driven Development

Be pro with errors

Questions?

Thoughts?

Suggestions?

Dev Humor

Thank you

Gaurav Sehrawat

Tech Consultant(Javascript/Python)

Full Stack Developer

Twitter: root3d

Github: igauravsehrawat