NodeJS or ExpressJS log [object Object] in my app??

May be: console.log(a.toString()) with typeof(a) == 'object'

So how can i see this object? And why object show here?

At first, you can only recognize where it comes from.

var realLog = console.error;
var fakelog = function(err) {
  if(!err) return;
  if(err==='[object Object]') return realLog.apply(console, [new Error(err)]);
  return realLog.apply(console, arguments);
};
console.error= fakelog;
console.warn= fakelog;
console.log= fakelog;
//

After knowing where it comes from, you can act with the object.