return undefined when i call JSON array?

Question

I am trying to create a JSON array inside another JSON array.
I think I did it right, but when I call the second array it returns undefined.

JSON file :

var files = [
    {"Files" : [
        {"file1" : "file1"},
        {"file2" : "file2"},
        {"file3" : "file3"}
    ]},

    {"Texts" : [
        {"file4" : "file4"},
        {"file5" : "file5"},
        {"file6" : "file6"}
    ]}
];

When I trying this command it works -

console.log(files[0]); // Works, returns the array

But when I trying this command it not working -

console.log(files[0][1]); // Not working, return undefined

I expect that this will return file2.

What I did wrong ?

EDIT : The script gets JSON file like that from the server, and the script need to loop through the JSON. So think about the names ( Files, Texts, file1, file2 etc.. ) as unknown..

Ilya · Accepted Answer · 2012-12-24 15:19:14Z

5

console.log(files[0]["Files"])  // will return array with file 1-3
console.log(files[0]["Texts"])  // will return array with file 4-6

or

console.log(files[0].Files)  // will return array with file 1-3
console.log(files[0].Texts)  // will return array with file 4-6

in you example files[0][1] work for json like this

var files = [
    [
        {"file1" : "file1"},
        {"file2" : "file2"},
        {"file3" : "file3"}
    ],
    [
        {"file4" : "file4"},
        {"file5" : "file5"},
        {"file6" : "file6"}
    ]
];

EDIT
in this case you can use next for-loop

for (var key in files[0])
{
   files[0][key] // here key is "Files", this will return files 1-3       
}

edited Dec 24, 2012 at 15:19

answered Dec 24, 2012 at 15:09

Ilya

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1 Comment

julian Over a year ago

The script gets JSON file like that from the server, and the script need to loop through the JSON. So think about the names as unknown..

Pointy · Accepted Answer · 2012-12-24 15:09:49Z

5

This:

console.log(files[0]);

does not log an array, it's the object that's the first element of the array. To get to the inner array, you have to get at the "Files" attribute of that object:

console.log(files[0].Files[1]);

What that will log is not just the string "file2", but the entire object, { file2: "file2" }. In JavaScript, object properties with string property names cannot be accessed by numeric index. That is, in the object:

{ "foo": "hello world" }

there simply is no [0] property. Arrays in JavaScript are also objects and can have string-named properties, but they're separate from the collection of numerically-indexed properties.

answered Dec 24, 2012 at 15:09

Pointy

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Comments

Fenton · Accepted Answer · 2012-12-24 15:10:06Z

2

The arrays are inside of the Files property:

console.log(files[0].Files[0]);
console.log(files[0].Files[1]);

answered Dec 24, 2012 at 15:10

Fenton

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