function - A while loop to add the digits of a multi-digit number together? (Javascript) -

i need add digits of number (e.g. 21 2+1) number reduced 1 digit (3). figured out how part.

however,

1) may need call function more once on same variable (e.g. 99 9+9 = 18, still >= 10) and

2) need exclude numbers 11 , 22 function's ambit.

where going wrong below?

var x = 123; var y = 456; var z = 789;  var numbermagic = function (num) {     var proc = num.tostring().split("");     var total = 0;     (var i=0; i<proc.length; i++) {             total += +proc[i];         };     };  while(x > 9 && x != 11 && x != 22) {     numbermagic(x);     }; } else {     xresult = x; };  console.log(xresult);  //repeat while loop y , z 

here problems code

var x = 123; var y = 456; var z = 789;  var numbermagic = function (num) {     var proc = num.tostring().split("");     var total = 0;     (var i=0; i<proc.length; i++) {         total += +proc[i]; // indentation want awry     }; // don't need ; - not show stopper     // you're not returning anything!!!! };  while(x > 9 && x != 11 && x != 22) {     numbermagic(x);      }; // ; not needed // because x never changes, above while loop go on forever } else { // else has no if     xresult = x; // if code right, x remains unchanged };  console.log(xresult); 

hope helps in way

now - here's solution works

var x = 123; var y = 456; var z = 789;  var numbermagic = function (num) {     while (num > 9) {         if (num == 11 || num == 22) {             return num;         }         var proc = num.tostring().split("");         num = proc.reduce(function(previousint, thisvaluestring) {             return previousint + parseint(thisvaluestring);         }, 0);     }     return num; }  console.log(numbermagic(x)); console.log(numbermagic(y)); console.log(numbermagic(z));