A Simple Example:
By calling the function this way, we are able to check if the function already exists in the template (in templates/MY_TEMPLATE/js folder) before using the Virtuemart internal (components/virtuemart/assets/js) folder.
In this example we load 'JOOMLAROOT/components/virtuemart/assets/js/jquery-ui.js' if this doesn't already exist in the template/js folder.
A Full Example:
Here, using all parameters, the complete name and path are splitted.
In this case we load the library externally. Therefore we have '//ajax.googleapis.com/ajax/libs/jqueryui' as 2nd parameter.
Setting a path does not permit to auto-overide this file with the template version
As mentioned before, the first parameter is the name used to compare the loaded files and must always be the exactly the same. Do not change it for the override library or you loose the benefit of being able to compare them.
Then using vmJsApi::js('jquery-ui.1.8.6') and vmJsApi::js('jquery-ui') has not the same Main name and simply does not prevent the reloading. Therefore you must always use same name for same library and change the parameter number 3 (in this case '1.8.16').
The last parameter used here is true and must be set if you want to use the minified version (this adds .min in the file name to load).
In this example we load '//ajax.googleapis.com/ajax/libs/jqueryui/jquery-ui.1.8.16.min.js' (http// is not needed for external load and permits to auto-load http or https revision from Google here in case of SSL)
The logic is the same but the path changes:
This loads the facebox.css, testing if the file exists in the template (in templates/MY_TEMPLATE/css folder) or if negative, loads it from the virtuemart css (components/virtuemart/assets/css folder).