As an exercise for myself to practice my JavaScript "skills" I'm trying to write a client-side filter. It should be able to filter "content blocks" as the user types. By "content block", I mean a list of DomElements that each contain at least one text node - it is possible that they contain more, and even a different amount of text nodes, nested inside other nodes, etc. I've thought of 2 approaches: On page initialization, scan all nodes and store all the text in some kind of Map or a tree. Simply iterate over every item and check whether it has the string to search/filter for. One could add performance here by caching, only filtering the current remaining items if text is added, etc. Obviously, if the number of nodes is really big, option 1 will take a while to build the 'index' but it will perform faster once it is built. Option 2 however will be available right on page load since no initialization is performed. But of course it will take longer to search. So my question is: what is the best approach here? And how would one implement 'caching' and/or 'index'?