Digging, Debugging

<witty subtitle here>

Hashtags: #digdebug #jqcon

Brian Arnold

@brianarn | randomthink.net

  • Senior Software Engineer @ Bazaarvoice
  • Previously: Lead Support & Software Engineer at SitePen
  • Dojo core committer
  • Lord of Waterdeep
  • Rock Band guitar expert


  • Non-technical tips
  • Understand the tools
  • Techniques

Non-technical Tips

Be open to learning

We are professional students

Learn JavaScript

No, really, learn the core

Read the spec, read JS: TDG, go beyond the good parts


Learn about DevTools

We'll talk more about this later

To the dev who has only a console.log, everything looks like a string

Rubber Duck

  • Colleagues
  • Friends at other shops
  • An actual rubber duck

Understand the tools

Command Line API

Originally pioneered in Firebug, now fairly ubiquitous

Feature support varies, learn your environment of choice

Moving between Elements and Console

  • $0
  • $_
  • inspect

Detailed viewing

  • console.*
  • dir
  • copy


  • debugger;
  • Breakpoints
  • Watch things

Other types of breaks

  • DOM Breakpoints
  • XHR Breakpoints


  • Fuzzy finder opening
  • Pretty printing
  • Breaking on some/all errors


  • Memory
  • Runtime


(Here there be hacks)

Use a style guide, damnit

Inconsistently written code SUCKS

Look into things like Idiomatic for a starting point, and EditorConfig to help enforce it

You don't write code for yourself, you write it for the moron who has to maintain it in a year.

More often than not, you are that moron.

Private Mode

Not just for hiding things

Extra Users

For when Private Mode isn't enough

Breakpoint Actions

Use and abuse of conditional breakpoints for fun and profit*

* There may not be profit

Crimes Against Production

Breakpoint abuse

`console.group` EXTREME!!1!

      .each(function (method) {
        var oldMethod = toWrap[method];

        toWrap[method] = function () {
          var groupName = identifier + ': ' + method;
          console.log('%s args: %o', method, arguments);

          var value = oldMethod.apply(this, arguments);

          console.log('%s return value: %o', method, value);

          return value;