superman.js

{
    shouldFlag: function(selectedIds) {
        // Assume don't flag
        var shouldFlagMessages = false;
        // Keep track of how many are flagged and not flagged
        var flaggedCount = 0;
        var unFlaggedCount = 0;

        // Get only the messages we care about
        var messagesInQuestion = [];
        for (var i = 0; i < this.messages.length; i++) {
            if (selectedIds.indexOf(this.messages[i].id) !== -1) {
                messagesInQuestion.push(this.messages[i]);
            }
        }

        // Determine the number of flagged messages vs. unflagged messages in the set
        for (var i = 0; i < messagesInQuestion.length; i++) {
            if (messagesInQuestion[i].flagged) {
                flaggedCount++;
            } else {
                unFlaggedCount++;
            }
        }

        // Only flag the messages if there are no flagged messages
        // OR there are messagesInQuestion present that are not flagged
        if (flaggedCount === 0 || unFlaggedCount !== 0) {
            shouldFlagMessages = true;
        }

        return shouldFlagMessages;
    }
}