javascript traverse json object

Question

I always think it's going to be easy... I plan to use the json below to build router objects. I put a console.log and so I could have a break point spot so I could try to figure out how to access the the object properties from the chrome console. It never goes into the for loop though.

The main question is how to properly turn the JSON into objects and how to access it's properties.

<script type="text/javascript">
    $(document).ready(function(){

        $.getJSON('JSON/data.json', function(json) {

            for (var i=0;i<json.length;i++){
                console.log("in for loop");
            }

        });
    });

</script>





{
"_id": {
    "$oid": "4f91f2c9e4b0d0a881cf86c4"
},
"DSC21": {
    "Router": {
        "online": [
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1"
        ],
        "bytes": [
            "59.5721304971465",
            "17014.1911069063",
            "14858.8518936735",
            "6875.20981475265",
            "15157.6891384625",
            "6363.47544785913",
            "29446.2111270486",
            "11517.9296243171",
            "27077.9747917112",
            "19867.79381695"
        ]
    }
},
"DSC22": {
    "Router": {
        "online": [
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1"
        ],
        "bytes": [
            "59.5721304971465",
            "17014.1911069063",
            "14858.8518936735",
            "6875.20981475265",
            "15157.6891384625",
            "6363.47544785913",
            "29446.2111270486",
            "11517.9296243171",
            "27077.9747917112",
            "19867.79381695"
        ]
    }
},
"DSC23": {
    "Router": {
        "online": [
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1"
        ],
        "bytes": [
            "59.5721304971465",
            "17014.1911069063",
            "14858.8518936735",
            "6875.20981475265",
            "15157.6891384625",
            "6363.47544785913",
            "29446.2111270486",
            "11517.9296243171",
            "27077.9747917112",
            "19867.79381695"
        ]
    }
},
"DSC24": {
    "Router": {
        "online": [
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1",
            "1"
        ],
        "bytes": [
            "59.5721304971465",
            "17014.1911069063",
            "14858.8518936735",
            "6875.20981475265",
            "15157.6891384625",
            "6363.47544785913",
            "29446.2111270486",
            "11517.9296243171",
            "27077.9747917112",
            "19867.79381695"
        ]
    }
}

}

Check this: $.getJSON('JSON/data.json', function(json) {console.log(json); ...} — gdoron
– gdoron, Commented Apr 21, 2012 at 18:31
Please read some introduction to JavaScript to learn how to work with objects and arrays. — Felix Kling
– Felix Kling, Commented Apr 21, 2012 at 18:55

Dennis · Accepted Answer · 2012-04-21 18:31:10Z

4

The variable json is already an object, but it is not an array, so a typical for-loop is insufficient. Since json.length is undefined, i<json.length fails on the first iteration and you skip over the loop.

for (var key in json) {
    // key is your DSCxxx
    // json[key] is the corresponding object
}

answered Apr 21, 2012 at 18:31

Dennis

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2 Comments

rd42 Over a year ago

Ahhh so it's an array of objects.

gdoron Over a year ago

You might want to see this comment of the OP...

Halcyon · Accepted Answer · 2012-04-21 18:33:34Z

3

JSON is natively available in JavaScript, you traverse it like you would traverse any object or array.

json["DSC21"]["Router"]["online"][0];    // 1
json.DSC21.Router.online[0];    // equivalent
json.DSC21.Router.online.0;    // INCORRECT

If you don't know the names of the properties and want to loop through them use the for .. in construction:

for (var key in json) {
    console.log(key);   // _id, DSC21, DCS22 etc..
    console.log(json[key]);    // { "$oid": "" }, { "Router": ".." } etc.
}

This does leave the hasOwnProperty issue, but it shouldn't be a problem if you're just reading JSON data.

answered Apr 21, 2012 at 18:33

Halcyon

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3 Comments

Felix Kling Over a year ago

"JSON is natively available in JavaScript" What does that mean? A JSON parser is natively available in JavaScript (since ES5) which converts JSON to objects/arrays, that's all.

Zeeshan Over a year ago

What if there are nested objects and strings inside how can you implement this solution in that specific case?

Halcyon Over a year ago

@xeeB Can you post your data structure and which properties you want to read?

mindandmedia · Accepted Answer · 2012-04-21 18:32:40Z

1

maybe you want to know how to iterate your objects?

here would be how to do that:

for( var key in json ){
   if( key != '_id'){
      var router = json[key].Router;
      for( var i = 0; i < router.online.length; i++ ){
        console.log(i + ' is online: ', router.online[i]==1?'true':'false');
      }
      etc...
   }
}

answered Apr 21, 2012 at 18:32

mindandmedia

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