Question

I’m creating an API that returns results as JSON. Is there a current best practice for whether we should include keys in the result when the value is null? For example:

{
    "title":"Foo Bar",
    "author":"Joe Blow",
    "isbn":null
}

or

{
    "title":"Foo Bar",
    "author":"Joe Blow"
}

Since the second is smaller I am leaning towards this style, but I’m not sure if there is a preferred style or not. From a client perspective it seems like both styles would be functionally equivalent. Any pros or cons to each?

Answer 1

The second will save a small amount on bandwidth, but if that were a concern you would also use indexed arrays instead of filling the JSON with keys. Clearly, ["Foo Bar","Joe Blow"] is much shorter than what you have now.

In terms of usability, I don’t think it makes any difference. In both cases, if(json.isbn) will skip to the else. There is usually no need to distinguish between null (no value) and undefined (no given value).