Should JSON include null values [closed]

I am a fan of always including null explicitly as that carries meaning.While omitting a property leaves ambiguity.

As long as your protocol with the server is agreed upon any of the above can work, but if you pass nulls from the server I believe that makes your APIs more flexible later.

Should also mention that javascript's hasOwnProperty function gives you further insight.

/* if true object DOES contain the property with *some* value */if( objectFromJSON.hasOwnProperty( "propertyName" ) )/* if true object DOES contain the property and it has been set to null */if( jsonObject.propertyName === null )/* if true object either DOES NOT contain the property   OR   object DOES contain the property and it has been set to undefined */if( jsonObject.propertyName === undefined )

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).

In JavaScript, null means something very different than undefined.

Your JSON output should reflect what is used and needed by your application in the specific context of using the JSON data.