node.js - Get error on database insert -

i'm using nodejs node-postgres module , have simple queries can't understand how can catch errors on insert queries. that's sample code:

 pg.connect(constring, function (err, client, done) {         client.query("insert foo(bar) values ('lol')");         res.json({'err':0,'message':'successful insert'}); }); 

i add res.json({'err':1,'message':'errror'}); in case of error during query.

due example in github page: https://github.com/brianc/node-postgres
screenshot: http://joxi.ru/k823gg6uvx3d2o

try this:

 pg.connect(constring, function (err, client, done) {    if(err) {      console.log('cannot connect!', err);      return;    }     client.query("insert foo(bar) values ('lol')", [], function(err, result) {       if(err) {         console.log('error: ', err);         res.json({'err':1,'message':'errror'});         return;       }       res.json({'err':0,'message':'successful insert'});    }); });