Deleting all paths != String1 or String2

I'm not quite sure how to phrase the syntax for this. Ultimately I want to delete all path in a document that don't have the name Ex1 or Ex2 or Ex3.

This is what I have so far

deletepaths();

function deletepaths() {
    if (!documents.length) return;
    var doc = activeDocument;
    for (var a = doc.pathItems.length - 1; a > -1; a--) {
        if (doc.pathItems[a].name == "Ex1") {
            return true;
        }
        if
        else(doc.pathItems[a].name == "Ex2") {
            return true;
        } else doc.pathItems[a].remove();
    }
}