Find value in Json by javascript

Question

I cant find one way to get this value ("comment") into json using javascript.

var myJSONObject = {
    "topicos": [{
        "comment": {
            "commentable_type": "Topico", 
            "updated_at": "2009-06-21T18:30:31Z", 
            "body": "Claro, Fernando! Eu acho isso um extremo desrespeito. Com os celulares de hoje que at\u00e9 filmam, poder\u00edamos achar um jeito de ter postos de den\u00fancia que receberiam esses v\u00eddeos e recolheriam os motoristas paressadinhos para um treinamento. O que voc\u00ea acha?", 
            "lft": 1, 
            "id": 187, 
            "commentable_id": 94, 
            "user_id": 9, 
            "tipo": "ideia", 
            "rgt": 2, 
            "parent_id": null, 
            "created_at": "2009-06-21T18:30:31Z"
        }
    }]
};

I'm trying a example like this:

alert(myJSONObject.topicos[0].data[0]);

Some body can help me?

The json is from Ruby On rails application, using render :json => @atividades.to_json

Tks a lot! Marqueti

rfunduk · Accepted Answer · 2009-11-09 23:40:30Z

13

~~Your JSON is formatted in such a way that it is very hard to read, but~~ it looks to me like you're looking for:

alert( myJSONObject.topicos[0].comment );

This is because there is no data key in the object given by ...topicos[0], but rather just the key comment. If you want further keys past that just continue like: obj.topicos[0].comment.commentable_type.

Update

To find out what keys are in topicos[0] you can take a couple approaches:

use a switch or if like:

var topic = myJSONObject.topicos[0];
if( topic.hasOwnProperty( 'comment' ) ) {
  // do something with topic.comment
}

You might have issues with cross browser compatibility here, so using a library like jQuery would be helpful, but in general you can map over the properties like so:
```
for( var key in myJSONObject.topicos[0] ) {
  // do something with each `key` here
}
```

edited Nov 9, 2009 at 23:40

answered Nov 9, 2009 at 21:39

rfunduk

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2 Comments

Mercurybullet Over a year ago

to take it a step farther, you could do something like: alert(myJSONObject.topicos[0].comment.commentable_type);

mmarqueti Over a year ago

Tks for the replies. I need to get the key "comment" string. Because I can receive another type too. Something like this: myJSONObject.topicos[0].people ou myJSONObject.topicos[0].support And then I will do some If to format the correct output. tks !

Greg · Accepted Answer · 2009-11-09 21:53:04Z

1

This should work:

alert(myJSONObject.topicos[0].comment);

If you want you can loop through like this:

for (var key in myJSONObject.topicos[0])
{
   alert(key);
   if (key == 'comment')
    alert(myJSONObject.topicos[0][key]);
}

edited Nov 9, 2009 at 21:53

answered Nov 9, 2009 at 21:41

Greg

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