node.js loop through object array - arrays

Question

I'm trying to store multiple objects from an array as a variable. I really hope that makes sense.
So, I am able to store one element of the array in a variable.
var data = msg.payload.data;
msg.payload = data.observations[0].clientMac;
return msg;
But instead of just the MAC from key 0, I want to loop through each key, grab the mac, and store it in a new array. I'm just not sure how to do that.
Below is a sample of how the data is formatted:
{
"apMac" : "aa:bb:cc:11:22:33",
"apFloors" : [],
"apTags" : [],
"observations" : [{
"ipv4" : null,
"location" : {
"lat" : 5.73212614236217,
"lng" : -5.01730431523174,
"unc" : 1.5059361681363623,
"x" : [],
"y" : []
},
"seenTime" : "2015-09-30T10:59:01Z",
"ssid" : null,
"os" : null,
"clientMac" : "bb:cc:dd:33:22:11",
"seenEpoch" : 1443610741,
"rssi" : 46,
"ipv6" : null,
"manufacturer" : "Hewlett-Packard"
}
]
}

Answer 1

data.observations is just an array of objects. There are many ways to iterate over an array. Here's one:
data.observations.forEach(function(item) {
console.log(item.clientMac);
});
Or, if you want to create an array of them, you can do this:
var macs = data.observations.map(function(item) {
return item.clientMac;
});
console.log(macs); // an array of clientMac properties
You can see documentation for array.map() and array.forEach().

Answer 2

You can also write:
for( var item in data.observations){
console.log(item.bla);
}
or
for(var index=0;index<data.observations.length;index++){
console.log(data.observations[index].bla);
}