Get a sticky random number in a often called function (Javascript) -

i making guess number machine, supported book 'html5 game programming dummies'. got stuck @ function random number called.

i tried put outside function, doesn't work, because number doesn't refresh when there no turns. tried put in first if statement, called first time, gives undefined error. any1 can me?

code:

var turns = 3;  function guess() {      var randnum = math.round(math.random()*100);      var input = document.getelementbyid('input').value;     var output = document.getelementbyid('output');      if(turns == 3) {         if(input == randnum) {             output.innerhtml = 'congratulations! thats right answer!';             turns = 4;         } else if(input > randnum) {             output.innerhtml = 'the number lower!';         } else {             output.innerhtml = 'the number higher!';         }         turns--;     } else if(turns == 2) {         if(input == randnum) {             output.innerhtml = 'congratulations! thats right answer!';             turns = 4;         } else if(input > randnum) {             output.innerhtml = 'the number lower!';         } else {             output.innerhtml = 'the number higher!';         }         turns--;     } else if(turns == 1) {         if(input == randnum) {             output.innerhtml = 'congratulations! thats right answer!';             turns = 3;         } else if(input > randnum) {             output.innerhtml = 'the number '+randnum+'. lost!';             turns = 3;         } else {             output.innerhtml = 'the number '+randnum+'. lost!';             turns = 3;         }     } } 

ps. code not optimalized. any1 have tips optimalize code? lot!

it took me little while work out asking here, think answer you're looking ...

add line outside function

var turns = 3; var randnum = math.round(math.random()*100); // 1  function guess() {     // ... 

and towards end of function:

    } else {         output.innerhtml = 'the number '+randnum+'. lost!';         turns = 3;     }     randnum = math.round(math.random()*100); // 1 } 

so you're setting random number when document loaded, , having global variable function can access. user attempts 3 times guess number between 1 , 100 (pretty unreasonable challenge), , when run out of 'turns', randnum gets reset new random number user keep on guessing.