json Object 2 string (javascript)

// implement JSON.stringify serialization
JSON.stringify = JSON.stringify ||
function(obj){
    var t = typeof(obj);
    if (t != "object" || obj === null) {
        // simple data type
        if (t == "string") 
            obj = '"' + obj + '"';
        return String(obj);
    }
    else {
        // recurse array or object
        var n, v, json = [], arr = (obj && obj.constructor == Array);
        for (n in obj) {
            v = obj[n];
            t = typeof(v);
            if (t == "string") 
                v = '"' + v + '"';
            else 
                if (t == "object" && v !== null) 
                    v = JSON.stringify(v);
            json.push((arr ? "" : '"' + n + '":') + String(v));
        }
        return (arr ? "[" : "{") + String(json) + (arr ? "]" : "}");
    }
};