Problem with enumerators in JSON

Hi colleagues,

The important word in Gregor's answer is “behind”, as he writes, “Behind Position.SUPERSCRIPT is actually a Number (…)”

Indeed, keep in mind that although Position.SUPERSCRIPT can easily coerce into a Number, this is actually not a Number in CS5 and later. In fact, that's an object of the class Enumerator.

  // The truth 'behind' enumerator instances
  // ---
  alert( typeof Position.SUPERSCRIPT );       // => object
  alert( Position.SUPERSCRIPT.__class__ );    // => Enumerator
  alert( Position.SUPERSCRIPT.toString() );   // => "SUPERSCRIPT"
  alert( +Position.SUPERSCRIPT );             // => 1936749411

As you can see, a quick way to retrieve the underlying number of any enumeraor, myEnum, is to use the shortcut +myEnum (which implicitly involves the .valueOf() method.)

• More detail on this topic can be found in IdExtenso's enum extension.

The reason I emphasize this point here is, an Enumerator instance shouldn't appear as such in a JSON stream. Better is to numerify it (+myEnum) if no better option is available, because you can later assign that number to any DOM attribute that expects such enumerator and this will work fine. By contrast, if you assign the string reflection—i.e, myEnum.toString()—this won't work. In your JSON stream, there is good chance that the object Position.SUPERCRIPT will mutely translates into its associated string at some point and without your knowledge due to implicit stringification…

• $$.JSON automatically coerces Enumerator instances into numbers. If you make it verbose, it provides graceful hints on the origin of that number:

// One of the advantages of using $$.JSON in InDesign
// ---
var obj = { myAttribute: Position.SUPERSCRIPT };
alert( $$.JSON(obj, 1/*verbose*/) );
// Output (stringified)
//----------------------
{
    "myAttribute" : 0x73707363 /* [spsc] */
}

Hope that helps.

@+

Marc