Let's take a look at how to run the script now.
Execute the build script with the config file we created in the previous example. Depending on your operating system (refer to the commands we just talked about):
./build.py example_1.cfg
You should see the output after running the command which informs you what the script is doing. In this case, it merged a total of 34 files and the final file size was just over 160 KB. That's a huge decrease from the original 920 KB!
We just run the build script and an OpenLayers.js file was produced. Depending on your own application, you would create a build script and specify the classes your code uses. Then, you would run the build script with that configuration file and copy the outputted OpenLayers.js file over to your production code base.
Doing it this way, you cut down the time users have to wait to load your page, as the file size will be smaller and take less time to download.