Cannot assign new value to array element - javascript -

i relatively new programming , new javascript/html/css (read on few tutorials) , having weird problem first script. (trying make sudoku solver) array puzzle contains: "3.542.81.4879.15.6.29.5637485.793.416132.8957.74.6528.2413.9.655.867.192.965124.8 " puzzle[0] = 3 puzzle[ 1 ] = . , on. puzzle represents unsolved sudoku puzzle digits 1-9 rep solved cells , . unsolved cells.
below code 1 of functions , there 4 alert messages in it. problem lies near message 4 puzzle[c+(9*r)] = nums[0]; shows puzzle[c+9*r] still contains . , not value of num[0] (in first case 6). declared outside of functions:

var puzzle = new array(); var options = new array(); var nums = new array(); var r = 0; var c = 0; var num=0; 

• function checknumber works fine *

• message 1: "puz conatians ."

• message 2: "nums length 1"
• message 3: "nums[0] 6"
• message 4: = "puzzle ." should "puzzle 6"

any appreciated! please let me know if need further clarify =]

function makeoptionsarray() {      // loop through 9x9 grid of sudoku r = row c = column     (r = 0; r < 9; r++) {         (c = 0; c < 9; c++) {             nums.length = 0; // reset array each new cell              if (puzzle[c + (9 * r)] == '.') { // if unknown cell                 alert("puz contains " + puzzle[c + 9 * r]); // message 1                 (num = 1; num <= 9; num++) {                     if (checknumber(num, r, c)) { // check digits 1-9                           nums.push(num); // keep track of possible values                          //for cell based on other known values on board                       }                 }                 options[c + (9 * r)] = nums; // used part & contain possible values unsolved cell                 alert("nums length " + nums.length); // message 2                        if (nums.length == 1) { // if 1 possible number add sudoku                     alert("nums[0] " + nums[0]); // message 3                     puzzle[c + (9 * r)] = nums[0];                     document.getelementbyid(c + 9 * r).innerhtml = nums[0];                     alert("puzzle " + puzzle[c + 9 * r]); //message 4                     makeoptionsarray(); // call function again updated puzzle (one less unknown cell)                  }                 if (nums.length == 0) { //if no possible options no solutions puzzle                     alert("no solutions");                     return true;                 } else {                     continue;                 }             }          }      } }