JS eval () method to process JSON strings

PHP Code snippet:

Public Function Demo () {$sql = ' select count (0) from table where id= '. $id;        if (! $mysql->getresult ($sql)) {echo json_encode (Array (' Code ' = 2));    Exit } Echo Json_encode (' code ' + 1, ' mes ' = ' Are you sure you want to change the Tablez information?    ‘)); Exit;}

jquery Code Snippet:

 $ ("#info_btn"). Click (function () {    $.get ('/dmeo?_t= '  + math.random (),  function (data) {            var jsondata =eval ("(" + data + ")");         //here eval () processing the JSON string why use two parentheses?         if (jsondata.code==1)  {             if (Confirm (jsondata.mes)) {                 $ ("#Table_info"). Show ();                 $ ("#Form_info"). Hide ();             }        }         if (jsondata.code==2)  {              $ ("#Table_info"). Show ();             $ ("Form _info "). Hide ();         }    });

The

JS eval () method processes the JSON string