Using string in referencing JSON object in request

Question

Using a fetch request to get some data. The JSON object path depends on a string variable. How would I convert the string into an object that can be referenced as an array in the path. Here's my code:

var path = 'bob';

fetch(request)
    .then(function(response) {
        if (!response.ok) {
            throw Error(response.statusText);
        }
        return response.json();
    }).then(function(json) {

        var data = json.message.path[0].text;

    }).catch(function(error) {
        console.log(error);
    });

JSON:

{
"message": {
    "bob": [
      {
        "name_id": "3351",
        "name": "bob",
        "text": "lorem ipsum"
      },
      {
        "name_id": "34562",
        "name": "bob",
        "text": "lorem ipsum2"
      }
    ]
}

Basically, path defines the correct object to be used in the dot notation. BUT - the object also has to be able to reference the array.

Any solutions?

What do you mean by "the object has to be able to reference the array"? Can you give a concrete example of the structure of `json` and `path`? — qxz, Aug 07 '16 at 00:08
The the JSON is organized, the path is an array and I need to get the first item in that array. But I can only reference the path by a string. See example code. — bounty, Aug 07 '16 at 00:10
In your example, `path` isn't an array, it's a string... Do you mean that you get a string representing a path, which you then want to convert into an array? — qxz, Aug 07 '16 at 00:13
Possible duplicate of [Dynamically access object property using variable](http://stackoverflow.com/questions/4244896/dynamically-access-object-property-using-variable) — melpomene, Aug 07 '16 at 00:13
Added the example JSON. Basically access 'bob' at the top level is determined by a string. But I need to be able to reference bob[0] in the object notation when I'm defining the data. — bounty, Aug 07 '16 at 00:17
Sorry, edited example. `path = 'bob'` `path` is the variable being predefined in the code in order to reference the correct data. — bounty, Aug 07 '16 at 00:19
But what would be the syntax for using it as an array? `json.message[path][0].text`? — bounty, Aug 07 '16 at 00:22
Yes, that's how you use arrays. Or `var tmp = json.message[path]; ... tmp[0]` - same result. — melpomene, Aug 07 '16 at 00:24

score 1 · Accepted Answer · answered Aug 07 '16 at 00:27

1

You could try using:

var data = json.message[path][0].text;

where path is the name of the object as you defined:

path = "bob";

answered Aug 07 '16 at 00:27

Akintayo Jabar

836
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13

qxz · Answer 2 · 2016-08-07T00:29:30.840

If you have a path variable in the format user.index, you could reference the corresponding message in your JSON like this:

path = path.split(".");
var name = path[0], index = path[1];
var data = json.message[name][index].text;

If path is "bob.1", data would become "lorem ipsum2"

json.message[name] evaluates to the array of messages. To index into that array, just put brackets after the value, like any other array: json.message[name][index], which is equivalent to (json.message[name])[index], which is equivalent to var array = json.message[name] then array[index].

Note that this solution does no error checking, and will throw an error if the given user isn't in json.message.

Using string in referencing JSON object in request

2 Answers2