Parsing JSON, return empty instead of undefined

Question

I'm hoping someone give provide some guidance on the below:

I am fetching JSON with something like this:

$.getJSON(jsonPath, function(returnedData){
...
});

The object returned will look something like this:

...
"skin": {
  "elapsedTextColor": "#ffffff",
  "autoHideControls": "false",
  "autoplay": "false",
  "muted": "false",
   ...
}

I make use of this data like this:

...
skin : {
  screenLogoImage : skinData['skinconfig'][0]['skin'].screenLogoImage,
  screenLogoUrl : skinData['skinconfig'][0]['skin'].screenLogoUrl,
  ...
},

When the value doesn't exist in the JSON, the set value is "undefined".

Is there a way to return an empty value if infact the value doesn't exist in the JSON?

For example, if in the JSON, screenLogoImage is not defined, how do I get

skinData['skinconfig'][0]['skin'].screenLogoImage

to return empty (so that the library that makes use of the configuration ignores it and uses the default value for that attribute)?

Any guidance is greatly appreciated.

`skinData['skinconfig'][0]['skin'].screenLogoImage || [your 'empty' value]` — Gavin, Nov 11 '16 at 18:32
I mean ignore the missing key. So if a key is not defined in the JSON then when I try to set that key, then it just ignores it since there is no key (instead of returning undefined). — ymdahi, Nov 11 '16 at 18:34
I'd go through skin and remove the undefined keys. there are a couple of ways to do this: http://stackoverflow.com/questions/25421233/javascript-removing-undefined-fields-from-an-object — skav, Nov 11 '16 at 18:35

guest271314 · Accepted Answer · 2016-11-11T18:47:04.373

1

You can use || OR operator

skin : {
  screenLogoImage : skinData['skinconfig'][0]['skin'].screenLogoImage || settings.screenLogoImage,
  screenLogoUrl : skinData['skinconfig'][0]['skin'].screenLogoUrl || settings.screenLogoUrl,
  ...
}

or for..in loop

var data = {... screenLogoImage: undefined};
var settings = {screenLogoImage:"/path/to/resource/"} 
for (var key in data) {
 if (data[key] === undefined) data[key] = settings[key]
}

skin : {
  screenLogoImage : skinData['skinconfig'][0]['skin'].screenLogoImage,
  screenLogoUrl : skinData['skinconfig'][0]['skin'].screenLogoUrl,
  ...
}

edited Nov 11 '16 at 18:47

answered Nov 11 '16 at 18:33

guest271314

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Thanks, this is probably the easiest solution to implement. A few months ago I didn't have to do it this way - if the key screenLogoUrl didn't exist in the JSON then it would be ignored when I tried to bring it in to an array. I'm using the approach you outlined to defined a default value to prevent an empty value. – ymdahi Nov 11 '16 at 18:49
1

You could also use `Object.keys(data).forEach(function(key) { ... })` – Gavin Nov 11 '16 at 18:54

score 0 · Answer 2 · answered Nov 11 '16 at 18:34

You can use the or operator if you want to give a fallback when defining things that might be undefined.

var screenLogoImage = skinData['skinconfig'][0]['skin'].screenLogoImage || "";

In this case, if it is undefined (or false), it will be empty string instead of undefined.

Parsing JSON, return empty instead of undefined

2 Answers2