Roll20 API: reveal command by class

gistfile1.js

var getByClasses = function(classes, criteria) {
    var graphics = findObjs({                              
      _pageid: Campaign().get("playerpageid"),                              
      _type: "graphic",                          
    });
    var cclasses = {};
    for (var i = 0, il = classes.length; i < il; i++) {
        cclasses['.'+classes[i]] = true;   
    }
    var output = [];
    _.each(graphics, function(item) {
        var item_name = item.get('name');
		if (criteria) {
			var matches_criteria = true;
			for (var clabel in criteria) {
				var cvalue = criteria[clabel];
				if (item.get(clabel) != cvalue) {
					return;
				}
			}
		}
        var item_classes = item_name.match(/\.\w+/);
        _.each(item_classes, function(cclass) {
            if (cclasses[cclass]) {
                output[output.length] = item;
            }
        });
    });
    return output;
}

var getRandomByClasses = function(classes, criteria) {
    var items = getByClasses(classes, criteria);
    if (!items.length) {
        return;
    }
    var item = items[_.random(0, items.length-1)];
    return item;
}

var getRandomByClass = function(klass, criteria) {
    return getRandomByClasses([klass], criteria)
}

var getByClass = function(klass, criteria) {
    return getByClasses([klass], criteria);
}

var processCommand = function(command, argv) {
	switch(command) {
        case '!reveal':
        case '!show':
            /*
            Usage: !reveal foo bar
            Result: 
              will find all graphics with a name that contains .foo or .bar and
              then move them to the objects layer. This may be useful for ambushes,
              cutscenes, etc.
            */
            _.each(getByClasses(argv), function(item) {
                item.set({
                    'layer': 'objects'
                });
            });
            break;
        case '!conceal':
        case '!hide':
            /*
            Usage: !conceal foo bar
            Result: 
              will find all graphics with a name that contains .foo or .bar and
              then move them to the gm layer. This may be useful for ambushes,
              cutscenes, etc.
            */
            _.each(getByClasses(argv), function(item) {
                 item.set({
                    'layer': 'gmlayer'
                });
            });
            break;
        case '!revealrandom':
        case '!showrandom':
            // Usage: !revealrandom foo bar
            // Result: picks a random item with .foo or .bar in the name and shows
            var item = getRandomByClasses(argv, {'layer':'gmlayer'});
            item.set({
                'layer': 'objects'
            });
            break;
        case '!concealrandom':
        case '!hiderandom':
            // Usage: !revealrandom foo bar
            // Result: picks a random item with .foo or .bar in the name and hides
            var item = getRandomByClasses(argv, {'layer':'objects'});
            item.set({
                'layer': 'gmlayer'
            });
            break;
        case '!alter':
        case '!change':
            // Usage: !alter foo bar > rotation=24.1 aura1_radius=5 aura1_color="#44FF00"
            // Result: changes properties of all graphics with .foo or .bar
            // Note that this is not a proper parser, so you need to keep it to 
            // a single space, don't forget the '>' character to separate the 
            // classes from the properties, and put quotes around strings.
            // Additionally, don't put spaces in values, as it will not work.
          
            var classes = [];
            var alterations = [];
            var found = false;
            
            for (var i = 0, il = argv.length; i < il; i++) {
                var klass = argv[i];
                if (klass == '>') {
                    found = true;
                    continue;
                }
                if (!found) {
                    classes[classes.length] = klass;
                } else {
                    alterations[alterations.length] = klass;
                }
            }
            alterations = alterations.join(' ');
            log(alterations);
            eval('var changes = ' + alterations);
            log(changes);
            _.each(getByClasses(classes), function(item) {
                item.set(changes);
            });
            
            break;
    }
}

on("chat:message", function(msg) {
    var argv = msg.content.split(' ');
    var command = argv.shift();
    if (msg.type != 'api') {
        return;
    }
    log(msg.content);
	return processCommand(command, argv);
});