Modifying snowplow js

HOME > SNOWPLOW SETUP GUIDE > Step 2: setup a Tracker > Javascript tracker > Modifying Snowplow.js

Overview

It may be necessary for you to make changes to snowplow.js. If you do, then you will also need to minify your updated snowplow.js prior to deploying it. This guide covers how to do this.

To continue with this guide, you will need the following

Access to a Unix-like command line with sed and the Java runtime installed
Familiarity with and access to [Git] [git]
The ability to install [YUI Compressor 2.4.2] yuic
Some level of technical ability ta2, where ta1 < ta2 < ninja

Once you have those ready, please read on...

1. Check out the source code

First please download the source code to your development machine:

$ cd ~/development
$ git clone http://github.com/snowplow/snowplow.git
...
$ cd snowplow/1-trackers/javascript/js/
$ ls
snowplow.js   sp.js         snowpak.sh

In the listing above, snowplow.js is the original JavaScript; sp.js is the minified version and snowpak.sh is a Bash shell script for performing the minification.

2. Update `snowplow.js`

Making changes to snowplow.js (and testing them) is out of scope of this document.

Once you have made your changes and tested them, you are ready to minify your new snowplow.js.

3. Install YUI Compressor 2.4.2

To minify the JavaScript, we use a bash shell script which in turn uses YUI Compressor 2.4.2. YUI Compressor depends on the Java runtime - we'll assume that you already have Java installed.

To install YUI Compressor 2.4.2:

$ sudo mkdir /opt/yui
$ cd /opt/yui
$ sudo wget http://yui.zenfs.com/releases/yuicompressor/yuicompressor-2.4.2.zip
$ sudo unzip yuicompressor-2.4.2.zip
$ sudo rm yuicompressor-2.4.2.zip

Just check that the required jarfile has now been installed:

$ file /opt/yui/yuicompressor-2.4.2/build/yuicompressor-2.4.2.jar
/opt/yui/yuicompressor-2.4.2/build/yuicompressor-2.4.2.jar: Zip archive data, at least v1.0 to extract

Now you're ready to minify snowplow.js.

4. Minify the JavaScript

Minification is handled by the bash shell script snowpak.sh, in the same folder as snowplow.js. snowpak.sh takes one argument, which is the path to the folder in which you installed YUI Compressor.

To run snowpak.sh is easy:

$ cd ~/development/snowplow/1-trackers/javascript/js/
$ ./snowpak.sh /opt/yui/yuicompressor-2.4.2

This will overwrite your existing sp.js.

A note: in theory it should be possible to use any JavaScript minifier or pipelining tool to minify the JavaScript - however, you would need to read through and understand what snowpak.sh is doing and make sure to recreate that same behaviour in your minification process.

5. Upload the minified JavaScript

Use your standard asset pipelining strategy to upload the minified sp.js JavaScript to your servers. Note that to avoid "mixed content" warnings, Snowplow expects the sp.js JavaScript to be available both via HTTP and via HTTPS.

6. Test your updated JavaScript

As a final step, you will want to just check that your customised sp.js JavaScript is working okay.

To do this, please follow the testing instructions at the end of the guide to [Integrating Snowplow tags directly onto your website] (Integrating Javascript tags onto your website#testing).