Removing duplicates from comma-separated list

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().joi开发者_开发问答n(',');

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

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 ,

You could do:

var duplicates = {};

poiSelectedList = $('#poiList li li.selected').map(function() { 
     var rel = $(this).attr('rel'); 
     if (duplicates[rel] !== true){
         duplicates[rel] = true;
        return rel;
   }
}).get().join(',');

While this is not short nor good-looking, it should be a fast way

var poiSelectedList='';
var tmp;
$('#poiList li li.selected').each(function() { tmp[$(this).attr('rel')]=1; });
var comma=0;
for(var i in tmp) if (tmp.hasOwnProperty(i)){
if(comma){poiSelectedList+=','}else{comma=1}
poiSelectedList+=i;
}

Use jQuery

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