What does it mean when I see [object Object] while trying to debug JSON?

Question

I have a sample message like:

<Contact>

   <FirstName>Rich</FirstName>

   ...more elements etc.

</Contact>

with code like this:

var contact = {};

if (message.checkNodeExists('/Contact/FirstName')){

  contact.firstName = message.getNode('/Contact/FirstName');

}

qie.debug("contact: " + contact);

the debug return this result: 

[path=1-2] - contact: [object Object]

What does [object Object] mean and how can I fix it?

Answer 1

This is due to the JSON object being converted to a string but the object does not overwrite the parent objects toString method.  Here is an example that implements a toString function on the contact:  

var contact = {};

contact.toString = function() { return this.firstName;};

if (message.checkNodeExists('/Contact/FirstName')){

   contact.firstName = '' + message.getNode('/Contact/FirstName');

}

qie.debug("contact: " + contact);

This returns:

contact: Rich

However, that is probably not what you really wanted to do just to debug it.  In this case just use JSON.stringify() like so:

var contact = {};

if (message.checkNodeExists('/Contact/FirstName')){

   contact.firstName = '' + message.getNode('/Contact/FirstName');

}

qie.debug("Stringified contact: " + JSON.stringify(contact));

The results:

Stringified contact: {"firstName":"Rich"}

Additionally, you might see [object null], [object, Function] etc.  In which case check out this link for more detail: http://stackoverflow.com/questions/4750225/what-does-object-object-mean

 

Also, in case you were wondering why the code above has:

'' +

after the equal sign, see this question: 

JSON.stringify() throws an exception