Using “whose” on arrays in Javascript for Automation

Question

Playing with the new JS for automation using Script Editor. I\'m getting an error on the final line of the following:

var iTunes = Application(\"iTunes\");
var s         


        

Answer 1

Based on the JavaScript for Automation Release Notes Mail.inbox.messages.whose(...) example, the following should work:

var iTunes = Application('iTunes');
var filtered = iTunes.sources.whose({name : 'Library'});

The apparent goal for the "special whose method" with "an object containing the query" is to be efficient by only bringing select items (or item references) from the OS X object hierarchy into the resulting JavaScript array.

However, ... the whose feature of JXA appeared to have some bugs in the earlier OS X v10.10 release.

So, since the array in question is small (i.e. 2 items), filtering can be done fast & reliably on the JavaScript side after getting the elements as a JS array.

Workaround Example 1

var iTunes = Application('iTunes');
var sources = iTunes.sources();
var librarySource = null;
for (key in sources) {
    var name = sources[key].name();
    if (name.localeCompare("Library") == 0) {
        librarySource = sources[key];
    }
}

Workaround Example 2

var iTunes = Application('iTunes');
var sources = iTunes.sources();
function hasLibraryName(obj) {
    var name = obj.name();
    if (name.localeCompare("Library") == 0) {
        return true;
    }
    return false;
}
var filtered = sources.filter(hasLibraryName);