ITS HTML Template - SAP Javascript

I would like to know where SAP has implemented the java script functions. I am trying to customize HTML Templates for pz02 and pz05 and am having problems. I would like to know where i could find documentation for functions like:

SAP_InputFiled

SAP_DynproLayerBegin etc

I do know that template has the following:

`include(~service="system", ~language="", ~theme="dm", ~name="TemplateLibraryDHTML.html")`

but where can i go to see the above. How can I customize SAP_InputField if I do not like. For example I tried to use a select html tag. i could send data to SAP but I could not get data into the field.