Following are examples of running js_objgc.d. This script reports on the garbage collection of Java objects. That is it will keep track of when resources are allocated to an object, and when resources are freed from an object. It is useful for providing information on when garbage collection is not working correctly, as this can cause the browser to have a memory leak. We trace object creation (+1) and destruction (-1), and provide a summary each second of the running tally of the object class and originating filename. Here we can see it running on Code/JavaScript/func_clock.html # js_objgc.d Tracing... Hit Ctrl-C to end. FILE TOTAL CLASS 2007 Sep 23 22:59:24 func_clock.html 1 Date FILE TOTAL CLASS 2007 Sep 23 22:59:25 func_clock.html 2 Date FILE TOTAL CLASS 2007 Sep 23 22:59:26 func_clock.html 3 Date FILE TOTAL CLASS 2007 Sep 23 22:59:27 func_clock.html 4 Date FILE TOTAL CLASS 2007 Sep 23 22:59:28 func_clock.html 5 Date FILE TOTAL CLASS 2007 Sep 23 22:59:29 browser.js 3 Function <null> 5 Function func_clock.html 6 Date <null> 7 MouseEvent FILE TOTAL CLASS 2007 Sep 23 22:59:30 browser.js 3 Function <null> 5 Function func_clock.html 7 Date <null> 10 MouseEvent FILE TOTAL CLASS 2007 Sep 23 22:59:31 <null> 1 Constructor <null> 1 HTMLBodyElement <null> 1 XPCNativeWrapper <null> 1 XPC_WN_ModsAllowed_Proto_JSClass browser.js 1 Array browser.js 1 XPCNativeWrapper popup.xml 1 Array func_clock.html 7 Date <null> 13 MouseEvent <null> 18 Function browser.js 20 Function FILE TOTAL CLASS 2007 Sep 23 22:59:32 <null> 1 BoxObject <null> 1 Constructor <null> 1 HTMLBodyElement <null> 1 NodeList <null> 1 UIEvent <null> 1 XPCNativeWrapper <null> 1 XPC_WN_ModsAllowed_Proto_JSClass <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 84ff45a <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 8befbba bookmarksMenu.js 1 Function browser.js 1 Array browser.js 1 XPCNativeWrapper popup.xml 1 Function scrollbox.xml 1 Function <null> 2 Event popup.xml 2 Array bookmarks.js 3 With firebug-service.js 3 Object bookmarks.js 6 Object bookmarks.js 6 XPCWrappedNative_NoHelper func_clock.html 8 Date firebug-service.js 10 Function <null> 15 MouseEvent bookmarks.js 19 Error browser.js 20 Function bookmarks.js 22 Function <null> 39 XPCWrappedNative_NoHelper <null> 44 Function <null> 60 RegExp <null> 191 XULElement [... 39 seconds deleted ...] FILE TOTAL CLASS 2007 Sep 23 23:00:10 <null> 1 HTMLBodyElement <null> 1 HTMLCollection <null> 1 TreeColumns <null> 1 XPCNativeWrapper <null> 1 XPC_WN_NoMods_Proto_JSClass <null> 1 XULTreeBuilder <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 84ff45a <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 8befbba <null> 1 chrome://global/content/bindings/tree.xml#treebody 84caa3a <null> 1 chrome://global/content/bindings/tree.xml#treebody 84e3a72 <null> 1 nsXPCComponents_Interfaces <null> 1 nsXPCComponents_Results bookmarksMenu.js 1 Function browser.js 1 Array browser.js 1 XPCNativeWrapper browser.js 1 XPC_WN_NoMods_Proto_JSClass nsUpdateService.js 1 XPC_WN_NoMods_Proto_JSClass nsUpdateService.js 1 nsJSCID popup.xml 1 Function scrollbar.xml 1 String scrollbox.xml 1 Function tree.xml 1 Array <null> 2 Constructor <null> 2 UIEvent <null> 2 XPC_WN_ModsAllowed_Proto_JSClass <null> 2 nsXPCComponents_Classes browser.js 2 nsJSCID browser.js 2 nsJSIID utilityOverlay.js 2 nsJSCID utilityOverlay.js 2 nsJSIID <null> 3 Array <null> 3 NodeList nsUpdateService.js 3 Array nsUpdateService.js 3 Object nsUpdateService.js 3 With utilityOverlay.js 3 Call tree.xml 4 Function utilityOverlay.js 4 Function nsUpdateService.js 7 nsJSIID nsUpdateService.js 15 Function bookmarks.js 22 Function text.xml 23 String <null> 36 BoxObject func_clock.html 42 Date bookmarks.js 57 With firebug-service.js 57 Object bookmarks.js 73 Error browser.js 78 Function popup.xml 82 Array bookmarks.js 114 Object bookmarks.js 114 XPCWrappedNative_NoHelper <null> 157 MouseEvent firebug-service.js 172 Function <null> 307 XPCWrappedNative_NoHelper <null> 388 RegExp <null> 488 Event <null> 876 XULElement <null> 1221 Function FILE TOTAL CLASS 2007 Sep 23 23:00:11 <missed> -94 Date <missed> -34 Function <missed> -4 MouseEvent <missed> -2 Array <missed> -1 HTMLBodyElement <missed> -1 HTMLCollection <missed> -1 XPCNativeWrapper <missed> -1 XPC_WN_ModsAllowed_Proto_JSClass <null> 0 Array <null> 0 HTMLBodyElement <null> 0 HTMLCollection <null> 0 RegExp <null> 0 TreeColumns <null> 0 UIEvent <null> 0 XPC_WN_NoMods_Proto_JSClass <null> 0 XULTreeBuilder <null> 0 nsXPCComponents_Classes <null> 0 nsXPCComponents_Interfaces <null> 0 nsXPCComponents_Results browser.js 0 Array browser.js 0 XPCNativeWrapper browser.js 0 XPC_WN_NoMods_Proto_JSClass browser.js 0 nsJSCID nsUpdateService.js 0 Array nsUpdateService.js 0 Function nsUpdateService.js 0 Object nsUpdateService.js 0 With nsUpdateService.js 0 XPC_WN_NoMods_Proto_JSClass nsUpdateService.js 0 nsJSCID nsUpdateService.js 0 nsJSIID scrollbar.xml 0 String text.xml 0 String tree.xml 0 Array utilityOverlay.js 0 Call utilityOverlay.js 0 Function utilityOverlay.js 0 nsJSCID <null> 1 NodeList <null> 1 XPCNativeWrapper <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 84ff45a <null> 1 chrome://global/content/bindings/menu.xml#menu-iconic 8befbba <null> 1 chrome://global/content/bindings/tree.xml#treebody 84caa3a <null> 1 chrome://global/content/bindings/tree.xml#treebody 84e3a72 bookmarksMenu.js 1 Function browser.xul 1 Function func_clock.html 1 Date popup.xml 1 Function scrollbox.xml 1 XULElement scrollbox.xml 1 nsJSIID <null> 2 Constructor <null> 2 XPC_WN_ModsAllowed_Proto_JSClass browser.js 2 nsJSIID scrollbox.xml 2 Function tree.xml 2 Function utilityOverlay.js 2 nsJSIID popup.xml 3 Array bookmarks.js 5 With firebug-service.js 5 Object <null> 6 Event <null> 6 MouseEvent bookmarks.js 9 XPCWrappedNative_NoHelper <null> 10 XPCWrappedNative_NoHelper bookmarks.js 10 Object browser.js 10 Function bookmarks.js 15 Function firebug-service.js 16 Function <null> 18 BoxObject bookmarks.js 75 Error <null> 79 Function <null> 315 XULElement ^C Just after time 23:00:10, garbage collection fired cleaning up many objects. The final output shows a much reduced object count including a negative count for objects created before this script was tracing. If over the period of several minutes an object type is still steadily increasing, then that would be of interest. Be patient, depending on the rate of object creation it can take over ten minutes for garbage collect to kick in.