HTML extensions: Getting values out of callbacks

I want to store a value from JSX in JS so I don't have to call evalScript all the time.

Is there a way to get a value out of a callback like this?

        var csInterface = new CSInterface();     evalout = "lcl";               csInterface.evalScript("$._ext_PPRO.testOnLoadedVar",     function (result)          {          evalout = result;          console.log("In testcb: evalout:"+evalout);          console.log("In testcb: result:"+result);          }     );     console.log("evalout: "+evalout);

The console output happens before the callback runs, so evalout equals "lcl". I've also tried the function as a named function, but the same thing happens. I think there is something basic that I'm missing.

Thanks,

Miles