Question

I am generating a comma-separated list out of the rel-attributes of several li-elements, using the map-function.

poiSelectedList = $('#poiList li li.selected').map(function() { return $(this).attr('rel'); }).get().join(',');

How can I assure that there are no duplicates inside my list?

Answer 1

You could make a cache like this:

var cache = [];
poiSelectedList = $('#poiList li li.selected').map(function() {
    var rel = $(this).attr('rel');
    if(cache.indexOf(rel) === -1) {
        cache.push(rel);
        return rel;
    } else {
        return undefined;
    }
}).filter(function(a, b) {
   return b !== undefined;
}).get().join(',');

---

Or, as patrick dw suggested, a more concise version:

var cache = [];
$('#poiList li li.selected').each(function() {
    var rel = $(this).attr('rel');
    if(!$.inArray(rel, cache)) {
        cache.push(rel);
    }
});
var poiSelectedList = cache.join(); // defaults to ,