AngularJs Filters

I'm writing a module, using a custom filter, and I noticed something weird. if I use console.log() inside a filter, it logs the value twice, even though I call it only once. Is there a way to log it only once? Does that mean the code inside the filter gets executed twice?

Here's the filter:

.filter('arrayToSentence', function($sce, $rootScope) {
    return function(array, index) {
        console.log(index);
        var i, word, sentence = '<span style="color:red;">';
        for (i = 0; i < array.length; i++) {
            if (i < array.length - 1) {
                sentence += array[i] + '&bnsp;';
            } else {
                sentence += array[i];
            }
        }
        sentence = sentence += '</span>'
        return $sce.sentence;
    }
})

The console.log(index) is logging twice. I need to make sure that my filter logic will not be duplicating anywhere, as further down I need to compare two arrays (the one being filtered, and another one to colour the differences between them, like missing word, or word mismatch).

[EDIT] It is pointed out to me that my question is a duplicate, of this Yet the original question doesn't answer how to avoid this issue, but I believe @defaultcheckbox provided a fulfilling answer.