JQ is an amazing tool when it solves your problems but I use it so rarely that it's hard to remember the syntax.
I'm expanding this page as I do new things in jq, doing them twice just to document them here so hopefully I can learn them in time and not have to look them up.
Select item from a list of objects by a key value in each object
A good example here is the Firefox logins.json file.
cat .mozilla/firefox/XXX.default-release/logins.json | \ jq '.logins | select(.hostname | contains("facebook"))'