Setting Global Variable within Javascript Asynchronous function -

i dont think understand callbacks , scope of javascript function. trying set response sentence, turns out undefined.

    function colortest(callback) {       models.victim.find({ victimsnumber: victimsnumber, active: true }, function(err, victim_data) {         var randcolor;         // color person said         if (victim_data[0].favcolor == null) {         // if null choose random color         randcolor = colors[math.floor(math.random() * colors.length)];       while (randcolor == thesms) {         randcolor = colors[math.floor(math.random() * colors.length)];       }       callback("incorrect. you're favorite color *"+ randcolor +"*. continue our cat facts *daily*.");     } else if (thesms == victim_data[0].favcolor) {       callback("good job! step 2 verification! favorite animal signed with?");     } else {       callback("incorrect. you're favorite color *"+ victim_data[0].favcolor +"*. continue our cat facts *daily*.");     }     // set color person said new color     models.victim.update({ _id: victim_data[0]._id}, {$set: {favcolor: thesms}}, function(err, result) {       if (err) { console.log(err); }     });     return response;   }); }  colortest(function(result) {     response = result; }); console.log("the color response is: " + response); 

colortest(function(result) {     response = result;     console.log("the color response is: " + response); }); 

this want.

you want console out response when response happens.

you consoling after function. but, since colortest has asynchronous calls, consoling occurs before callback function invoked.