Filtering records using javascript in subgrid or a view is unsupported and doesnt work hence here is how you can/should filter subgrid records using a plugin.
Recently we had a requirement to filter sub grid on one of the forms. We thought of using Plugin on Retrieve Multiple for this.
Here we were showing Opportunity Sub Grid on Account form.
So we created a view for Opportunity that will be used as Sub Grid. Used it as Related Record Sub Grid so that we can have the GUID of the Account record being passed to the plugin.
The problem we faced à Sorting and Paging stopped working for the Sub Grid.
http://crmtipoftheday.com/2015/10/05/limitations-of-retrieve-plugins/v
Hope it helps..
Passion Dynamics 