Check for values inside an array of objects from a json file

Question

I'm working in JavaScript and I have a json file with info from Twitter. I have no problem accesing it using something like: var content = data.text; so I can use it to change a div using innerHTML. Now, I'm also trying to check if certain hashtag is present (to fire a video). Now, I have a variable called data that using the .getJSON method stores the info from the JSON file.

I can access properties like time_zone easily using data.user.time_zone but thing like the hashtags are inside an array of objects and I don't know how to acces, for instance the 'text'.

This is the '.json' (I edited some info because it was too long).

{
"user": {
    "following": null,
},
"in_reply_to_screen_name": null,
"entities": {
    "user_mentions": [],
    "urls": [],
    "trends": [],
    "symbols": [],
    "hashtags": [
        {
            "text": "fuego",
            "indices": [
                25,
                31
            ]
        },
        {
            "text": "primaLED",
            "indices": [
                32,
                41
            ]
        }
    ]
},
"contributors": null,
}

I found some "solutions" but none are working, I'm new to programing so I'm really lost.

Without a example of what you have tried we cant really help you. But here is a thread on how to do it. http://stackoverflow.com/questions/4935632/how-to-parse-json-in-javascript — marsh, Sep 12 '14 at 18:09
This is not a valid JSON file, which in this case would need to begin with a `}` and end with `}`. Once that's solved, what do you mean by "return the value of test (two elements) as a string"? Concatenated? As an array? — , Sep 12 '14 at 18:14
@daviestar Sorry, yes the updated question is not the same that before but is more adecuated to the title of the question. The problem remain the same, accesign the data inside the object in an array of objects. Anyway I will take in concideration this, I made this question in a hurry. sorry. — Sergio, Sep 13 '14 at 16:45

daviestar · Answer 1 · 2014-09-12T19:00:50.877

Ok, this answer is going to skim over some details, as what you are asking is quite a broad subject to explain fully. This should give you plenty of clues, and also a working answer.

First of all, you'll need to give the JSON object a name so you can reference it, something like this:

var json = {
    "entities": {
        "hashtags": [
            {
             "text": "fire",
             "indices": [
                        25,
                        31
                    ]
                },
                {
              "text": "water",
              "indices": [
                        32,
                        41
                    ]
                }
        ]
    }
};

Or if you are getting the JSON from an API with jQuery, something like this:

var json;
$.getJSON('http://www.domain.com/api', function(data) {
    json = data;
});

then, you need to look at what is an object {}, and what is an array [] in the JSON. As in my example below, you'll see I traverse an object with 'dot notation', ie. json.entries.hashtags. And I loop through an array, ie. for(...) and create an index i. I can then use that index to complete the traversal, ie. json.entries.hashtags[i].

var array = [];
for(var i = 0, hashtag; hashtag = json.entities.hashtags[i]; i++) {
    array.push(hashtag.text);
}
console.log(array);  // ["fire", "water"]

console.log(array[0]); // "fire"

console.log(array[1]); // "water"

Here I loop through the hashtags array in the JSON, and pick out the value of text and create my own array. This is generally the best way to go, especially if the JSON is out of your control - it could contain 1 hashtag, or 1000.

Pro tip: If I wanted to access just one of those properties and not loop, I could do it like this:

console.log(json.entities.hashtags[0].text); // "fire"
console.log(json.entities.hashtags[1].text); // "water"

Edit

Here is how you can test for a certain hashtag and act on it:

var array = [];
var fire = false;
for(var i = 0, hashtag; hashtag = json.entities.hashtags[i]; i++) {
    if(hashtag.text === "fire") {
        fire = true;
    }
}
if(fire) {
    // do stuff
}

Check for values inside an array of objects from a json file

1 Answers1