Sudoku Solver (easy level)

gistfile1.js

    function complete(data) {
        var result = true;
        var sum;
        for ( var i = 0; i < 9; i++ ) {
            sum = 0;
            for ( var j = 0; j < 9; j++ ) {
                sum += data[i * 9 + j];
            }
            if ( sum != 45 ) {
                result = false;
                break;
            }
        }
        return result;
    }

    var __checker = [1,2,3,4,5,6,7,8,9];
    function basicsud(s) {
        var stillchanging = true;
        while ( stillchanging ) {
            stillchanging = false;
            for ( var i = 0; i < 81; i++ ) {
                if ( s[i] == 0 ) {
                    var check = {};
                    var row = Math.floor(i / 9);
                    var col = i % 9;
                    var in_row = Math.floor(row / 3) * 3;
                    var in_col = Math.floor(col / 3) * 3;

                    for ( var j = 0; j < 9; j++ ) {
                        check[s[row * 9 + j]] = 1;
                        check[s[j * 9 + col]] = 1;
                        check[s[(in_row + Math.floor(j / 3)) * 9 + in_col + (j % 3)]] = 1;
                    }

                    var m = __checker.filter(function(elem, index, arr) {
                        return !check.hasOwnProperty(elem);
                    });

                    if ( m.length == 0 ) {
                        return null;
                    }
                    else if ( m.length == 1 ) {
                        s[i] = m[0];
                        stillchanging = true;
                    }
                }
            }
        }
        return s;
    }

    function solver(s) {
        var s1 = basicsud(s);
        if ( s1 == null ) {
            return null;
        }

        if ( complete(s1) ) {
            return s1;
        }
        else {
            var stack = [];
            for ( var i = 0; i < 81; i++ ) {
                if ( s1[i] == 0 ) {
                    var check = {};
                    var row = Math.floor(i / 9);
                    var col = i % 9;
                    var in_row = Math.floor(row / 3) * 3;
                    var in_col = Math.floor(col / 3) * 3;

                    for ( var k = 0; k < 9; k++ ) {
                        check[s1[row * 9 + k]] = 1;
                        check[s1[k * 9 + col]] = 1;
                        check[s1[(in_row + Math.floor(k / 3)) * 9 + in_col + (k % 3)]] = 1;
                    }

                    var m = __checker.filter(function(elem, index, arr) {
                        return !check.hasOwnProperty(elem);
                    });

                    if ( m.length > 2 ) {
                        for ( var l = 0; l < m.length; l++ ) {
                            stack.push($.toJSON(s1));
                            s1[i] = m[l];
                            var s2 = solver(s1);
                            if ( complete(s2) ) return s2;
                            s1 = $.parseJSON(stack.pop());
                        }
                    }
                }
            }
        }
        return null;
    }