how to find out what keys are in a json message

[vince_w]

anyone know if it's possible to find out what keys are present in a json message?

for example, if the json message is

{
"firstName": "John",
"lastName": "Smith",
"address": {
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": 10021
},
"phoneNumbers": [
"212 555-1234",
"646 555-4567"
]
}

i need to get firstName, lastName, address, and phoneNumbers.

[M-M-J]

Isn't this "message" stored in a variable?

[vince_w]

hi mmj. can you elaborate? i'm not sure what that means.

(the JSON data/message is sent from the server back to the browser that requests it)

[ArunB]

try

for(key in <<JSON object name>>) {
alert(key);
}

[M-M-J]

hi mmj. can you elaborate? i'm not sure what that means.

(the JSON data/message is sent from the server back to the browser that requests it)

You are evaling in then, right?

var data = eval(serverResponse);
if (data.firstName)
//
if (data.lastName)
//
 
//etc...

[ArunB]

anyone know if it's possible to find out what keys are present in a json message?

for example, if the json message is

{
"firstName": "John",
"lastName": "Smith",
"address": {
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": 10021
},
"phoneNumbers": [
"212 555-1234",
"646 555-4567"
]
}

i need to get firstName, lastName, address, and phoneNumbers.

If this is response from Server, use eval() function on client side. But this eval() function is not suggestible. Use JSON.parse (Download JSON.js from http://www.json.org/).

If it (the code you are displaying) is a object (already evaluated or is on client side, not received from server) then to find keys in this JSON object, use

for(key in <<JSON Object>>)
{
    alert(key); //key is the key in JSON object
}

I think, this will help you.

[seansullivan]

These guys are right, if you don't know what your keys are, you need to loop through the object (with a for in loop) and grab the keys in this manner.

Prototype JS also provides an Object.keys() method that will return an array of the keys.

When you say "i need to get firstName, lastName, address, and phoneNumbers.", it almost sounds to me like you are trying to access the values in the object. Here's how you do so.

If your Object is defined as,

var userInfo = {"firstName": "John", "lastName": "Smith", "address": {"streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": 0021}, "phoneNumbers": ["212 555-1234","646 555-4567"]};

You can access these values via their keys.

var firstName = userInfo.firstName;
var lastName = userInfo.lastName;
var address = userInfo.address;
var phone1 = userInfo.phoneNumbers[0];
var phone2 = userInfo.phoneNumbers[1];

[vince_w]

thanks guys. that works! this is what i ended up doing:

function listMarkers(url) {
	var request = google.maps.XmlHttp.create();
	request.onreadystatechange = function() {
		if (request.readyState == 4) {
			var assemblies = eval( request.responseText );
			for (var i = 0 ; i < assemblies.length ; i++) {
				var assembly = assemblies[i]
			        for(key in assembly) {
				    alert(key);
			        }
			}
		}
	}
	request.open('GET', url, true);
	request.send(null);
}

[vince_w]

out of curiosity, anyone know if it's possible to get the keys without using a for in loop?

for example, instead of

for(key in assembly) {
alert(key);
}

something like

alert(assembly[0]); //doesn't work
alert(assemby.key); //doesn't work

[ArunB]

Check, alert(assemby[key]); will work.

[vince_w]

Check, alert(assemby[key]); will work.

thanks ArunB - i was actually wondering if this could be done without using a for-in loop.

[M-M-J]

thanks ArunB - i was actually wondering if this could be done without using a for-in loop.

No, if you don't know the name of the object's properties than you will have to use a for in loop.