Mastering OpenLayers 3

Debugging the code

As you will have noticed, there was a third file in the OpenLayers 3 folder discussed at the beginning of the chapter (js/ol3-3.11.0). This file, named ol-debug.js, is the uncompressed source file, in which the library is concatenated with all of its dependencies. We will use this file for two purpose in this book. Now, we will use it for debugging. First, open up ch01_simple_map.js. Next, extend the init function with an obvious mistake:

var geometry = new ol.geom.Point([0, 0]);
vectorLayer.getSource().addFeature(geometry);

Don't worry if you can't spot the error immediately. That's what is debugging for. Save this extended JavaScript file with the name ch01_error.js. Next, replace the old script with the new one in the HTML ...