Check if array exists in json Javascript/Jquery

Question

I have a json file from the twitter api. Sometimes it does have the media[0] array and sometimes it doesnt. If it does i want to add the array to another array so it reminds it otherwise i want it to check the next one.

this is what i tried but it didnt work fine yet.

if(twitter.statuses[key].entities.media[0].media_url!=="Uncaught TypeError: Cannot read property '0' of undefined"){
    console.log(twitter.statuses[key].entities.media[0].media_url);
}

It keeps giving the error: Uncaught TypeError: Cannot read property '0' of undefined if the media array doesnt exist otherwise it works fine and goes further.

Does someone know how to fix this?

Thanks for helping!

leopik · Accepted Answer · 2014-10-02 07:31:19Z

2

You're getting the error because you want to retrieve first element of ... nothing (twitter.statuses[key].entities.media[0]; media is already a null and you can't access first element of null)

Try checking with

if (typeof twitter.statuses[key].entities.media != "undefined") {
    ...

answered Oct 2, 2014 at 7:31

leopik

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1 Comment

Stefan Over a year ago

Thanks this worked i kept trying this with media[0] instead of media thanks for the help

Jean-Karim Bockstael · Accepted Answer · 2014-10-02 07:56:20Z

2

An undefined property has the undefined type and value, you can check against it like this:

if (twitter.statuses[key].entities.media !== undefined) {
    // ...
}

or like this:

if (typeof twitter.statuses[key].entities.media !== "undefined") {
    // ...
}

edited Oct 2, 2014 at 7:56

answered Oct 2, 2014 at 7:32

Jean-Karim Bockstael

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2 Comments

Stefan Over a year ago

this doesnt work media[0] gives the same error as above but without the [0] it works fine thanks!

Jean-Karim Bockstael Over a year ago

I shouldn't post answers before coffee… fixed.

Alberto De Caro · Accepted Answer · 2014-10-02 07:37:12Z

0

I suggest you to always initialize variables to check null or undefined values. In your case:

var media0 = twitter.statuses[key].entities.media[0] || null;
if(media0 != null){
    if(media0.media_url != null)
       console.log(twitter.statuses[key].entities.media[0].media_url);
    else
       console.log('twitter.statuses[key].entities.media[0].media_url is null or not defined');
}
else
    console.log('twitter.statuses[key].entities.media[0] is null or not defined');

answered Oct 2, 2014 at 7:37

Alberto De Caro

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