🚀 go-pugleaf

Various specifier forms from AppleScript are available as methods in JavaScript, with the only exception of "whose". They have the (speed) advantage of being evaluated within the application rather than within the scripting engine.

You can simulate the behaviour in JavaScript with the following snippet:

// the following line makes the PageItems object available
app.activeDocument.pageItems;
PageItems.prototype.itemWhose = function (f)
{
	var result = [];
	for( var i=0; i<this.length; i++ ) 		if( f.apply(this.item(i)) ) 			result.push(this.item(i)); 	return	result; }

// use it like here:
a1 = app.activeDocument.pageItems;
a2 = a1.itemWhose( function() { return this.label=="my label" } );