Some form of catch guards have been implemented in Firefox for over a decade, so if you were running SpiderNode, you could use them right now. try {

Some form of catch guards have been implemented in Firefox for over a decade, so if you were running SpiderNode, you could use them right now. try { (17).toString(42); } catch (ex if ex instanceof RangeError) { console.log("caught"); } catch (ex) { console.log("handling something else"); } The if's clause has standard standard conditional semantics, so you can use any expression there; you aren't limited to selecting on the exception's prototype: try { throw new Error("whatever"); } catch (ex if ex.message == "whatever") { console.log("caught"); }