up vote 2 down vote favorite

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!

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4 Answers

up vote 4 down vote accepted

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 in jsonData.counters) {
    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 index of the current loop, not the actually 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).

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1  
If he uses a library that supports a cross-browser parseJSON function, he should use that. Also, you repeat the loop mistake. – Bergi Apr 3 '12 at 11:05
thanks @musefan . Worked like a charm – maephisto Apr 3 '12 at 11:10
up vote 3 down vote

You should post the error message you're getting when posting an error.

That said, doesn't look like there's anything wrong with your json parsing, you just don't know yet how loops work.

for (var counter in jsonData.counters) {
    console.log(jsonData.counters[counter].counter_name);
}

This in itself can cause issues, if the array prototype is overloaded. Therefore, this is actually a better syntax:

for (var i=0; i<jsonData.counters.length; i++) {
    console.log(jsonData.counters[i].counter_name);
}
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Thank you @Evert! – maephisto Apr 3 '12 at 11:11
up vote 1 down vote

In a for-in-loop the running variable holds the property name, not the property value.

for (var counter in jsonData.counters) {
    console.log(jsonData.counters[counter].counter_name);
}

But as counters is an Array, you have to use a normal for-loop:

for (var i=0; i<jsonData.counters.length; i++) {
    var counter = jsonData.counters[i];
    console.log(counter.counter_name);
}
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up vote 0 down vote

You should use a datastore and proxy in ExtJs. There are plenty of examples of this, and the JSON reader automatically parses the JSON message into the model you specified.

There is no need to use basic Javascript when using ExtJs, everything is different, you should use the ExtJs ways to get everything right. Read there documentation carefully, it's good.

By the way, these examples also hold for Sencha Touch (especially v2), which is based on the same core functions as ExtJs.

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