Из-за чего возникает переполнение стека?

function db_prepare(table, columns){
    var weight = 0;
    var is = Core.dbcfg_tables.indexOf(table);
    if(is){
        weight = 1;
    }
    if(columns != undefined){
        var i;
        for(i in columns){
            i = columns[i].column;
            try{
                if(Core.dbcfg_structures[table].columns.indexOf(i) != undefined){
                    if(weight > 0){
                        weight = 2;
                    }else{
                        weight = 1;
                    }
                }else{
                    if(weight > 0){
                        weight = 1;
                    }else{
                        weight = 0;
                    }
                }
            }catch(Ex){
                if(weight > 0){
                    weight = 1;
                }else{
                    weight = 0;
                }
            }
        }
    }
    if(columns != undefined){
        if(weight < 2){
            return false;
        }else{
            return true;
        }
    }else{
        if(weight < 1){
            return false;
        }else{
            return true;
        }
    }
}