I would like to set a variable with the following function setDef().
My example do not work. What I have to do?
    var defs = {
      title: document.title,
      action:   "pageview"
    };
    var setDefs = function(a,b) {
       defs.a= b;     // this: defs.title = b; is working.
    };
    setDefs("title","test");
 
    