Javascript how to parse JSON array

Question

I'm using Sencha Touch (ExtJS) to get a JSON message from the server. The message I receive is this one :

{
"success": true,
"counters": [
    {
        "counter_name": "dsd",
        "counter_type": "sds",
        "counter_unit": "sds"
    },
    {
        "counter_name": "gdg",
        "counter_type": "dfd",
        "counter_unit": "ds"
    },
    {
        "counter_name": "sdsData",
        "counter_type": "sds",
        "counter_unit": "   dd       "
    },
    {
        "counter_name": "Stoc final",
        "counter_type": "number    ",
        "counter_unit": "litri     "
    },
    {
        "counter_name": "Consum GPL",
        "counter_type": "number    ",
        "counter_unit": "litri     "
    },
    {
        "counter_name": "sdg",
        "counter_type": "dfg",
        "counter_unit": "gfgd"
    },
    {
        "counter_name": "dfgd",
        "counter_type": "fgf",
        "counter_unit": "liggtggggri     "
    },
    {
        "counter_name": "fgd",
        "counter_type": "dfg",
        "counter_unit": "kwfgf       "
    },
    {
        "counter_name": "dfg",
        "counter_type": "dfg",
        "counter_unit": "dg"
    },
    {
        "counter_name": "gd",
        "counter_type": "dfg",
        "counter_unit": "dfg"
    }

    ]
}

My problem is that I can't parse this JSON object so that i can use each of the counter objects.

I'm trying to acomplish that like this :

var jsonData = Ext.util.JSON.decode(myMessage);
for (var counter in jsonData.counters) {
     console.log(counter.counter_name);
 }

What am i doing wrong ? Thank you!

Answer 1

Javascript has a built in JSON parse for strings, which I think is what you have:

var myObject = JSON.parse("my json string");

to use this with your example would be:

var jsonData = JSON.parse(myMessage);
for (var i = 0; i < jsonData.counters.length; i++) {
    var counter = jsonData.counters[i];
    console.log(counter.counter_name);
}

Here is a working example

EDIT: There is a mistake in your use of for loop (I missed this on my first read, credit to @Evert for the spot). using a for-in loop will set the var to be the property name of the current loop, not the actual data. See my updated loop above for correct usage

IMPORTANT: the JSON.parse method wont work in old old browsers - so if you plan to make your website available through some sort of time bending internet connection, this could be a problem! If you really are interested though, here is a support chart (which ticks all my boxes).