meiro

fields    =  "#S######.#";
var width = fields.length;
fields    += "......#..#";
fields    += ".#.##.##.#";
fields    += ".#........";
fields    += "##.##.####";
fields    += "....#....#";
fields    += ".#######.#";
fields    += "....#.....";
fields    += ".####.###.";
fields    += "....#...G#";

var answers = [];
var walk = function(i,len,fields){
    fields[i] = "*";
    $.each([i-width,i-1,i+1,i+width],function(n,m){
        if(0 === (i % width) && 1 === n ){return}; //right-end 
        if((width - 1) === (i % width) && 2 === n ){return}; //left-lend
        if("."===fields[m]){walk(m,len+1,fields.slice(0))};
        if("G"===fields[m]){answers.push(len+1)};
    });
};

walk(1,0,fields.split(new RegExp("")));
console.log(Math.min.apply(null, answers));