Improving WordPress Theme Development Using Parker, Part 1

Lately, I’ve been playing with a CSS analysis tool called Parker created by Katie Fenn. Parker examines your stylesheet and gives a treasure trove of metrics. While some of these metrics are merely interesting factoids (like the number of CSS rules), others offer constructive criticism for improvement. The general philosophy behind using Parker is to create more maintainable CSS by simplifying your stylesheet.

Harry Roberts, of, has an excellent write-up about using Parker. He explains some of the options and offers some ideal scores to shoot for, which I’ll list and explain below. WordPress developers will need additional code in themes for adding classes in code generated by WordPress itself, like menus.

In my recent tests, I used Parker on my fork of the _s starter theme and made tweaks based on the results. I’ve based every project over the past two years on _s and advise anyone learning theme development to start there. For this post, I’m going to start with the current version of _s (not my fork) and optimize _s to get better scores from Parker.

Parker Setup

Before performing any of the following steps, you’ll need to install Parker and its dependencies. Parker runs from the command line, so you’ll need to open your favorite terminal app. I’m on a Mac, so I’ll be using Terminal. I’ll provide the instructions here for installing everything on a Mac, sorry Windows peeps. if you need assistance or run into difficulties with installing any particular thing, visit that tool’s site or try StackExchange. Here’s what you’ll need to install to follow along:

  • Xcode dev tools
  • Homebrew
  • node.js & npm
  • Parker
  • _s

Install Xcode and the Developer Tools

Open Terminal and hit enter after typing/pasting:

xcode-select --install

This should open an application installer wizard for the developer tools. Go through the prompts and install the package. (Source: OS X Daily)

Install Homebrew

Once that’s finished, install Homebrew, which makes installing packages on OS X easier. In Terminal, hit enter after typing/pasting:

/usr/bin/ruby -e "$(curl -fsSL"

This script installs Homebrew. It will ask for confirmation that you want to install it. Follow the prompts. (Source: Homebrew)

Install node.js and npm

Once Homebrew is installed, installing node.js is fairly simple. In Terminal, hit enter after typing/pasting (Source: George Ornbo):

brew install node

Install Parker

Next, install Parker. In Terminal, hit enter after typing/pasting:

npm install -g parker

The “-g” installs Parker globally, so you can access it from anywhere in your system (rather than just inside a specific project or folder). (Source: Harry Roberts)

Copy _s

Lastly, we’ll need a copy of _s. Open Finder and decide where you want to save _s. This can be any folder; I put my copy of _s in Dropbox. In Terminal type/paste:


Be sure to leave a space at the end! Drag your work folder from Finder to Terminal. This puts the path to your work folder into Terminal. Hit enter and your working directory in Terminal changes to your work folder. Use git to clone the _s repo from Github and work with it on your computer. In Terminal, hit enter after typing/pasting:

git clone

Wrapping Up

In the next post, we’ll use Parker to create a baseline measurement so we can see if any of our optimizations are effective. I’ll also explain what each  result in the report from Parker means.

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