Preferences

From PlainOldWebserver

Preferences can be read at the address, 'about:config'. These will not show there, because clearUserPref() is called right after reading.

 <?sjs
   var prefs = Components.classes["@mozilla.org/preferences-service;1"]                
      .getService(Components.interfaces.nsIPrefBranch);
   prefs.setBoolPref("my_extension.trash_bool",  true);
   if(prefs.getPrefType("my_extension.trash_bool") == prefs.PREF_BOOL) {
     var b = prefs.getBoolPref("my_extension.trash_bool");
     document.writeln("b is "+b);
     prefs.clearUserPref("my_extension.trash_bool");
   }
   prefs.setIntPref("my_extension.trash_int", 5);
   if(prefs.getPrefType("my_extension.trash_int") == prefs.PREF_INT) {
     var i = prefs.getIntPref("my_extension.trash_int");
     document.writeln("i is "+i);
     prefs.clearUserPref("my_extension.trash_int");
   }
   prefs.setCharPref("my_extension.trash_char", "hello prefs!");
   if(prefs.getPrefType("my_extension.trash_char") == prefs.PREF_STRING) {
     var c = prefs.getCharPref("my_extension.trash_char");
     document.writeln("c is "+c);
     prefs.clearUserPref("my_extension.trash_char");
   }
 ?>

Result:

 b is true
 i is 5
 c is hello prefs!