Question

I have an array such as:

var aos = ["a","a","b","c","d"];

and I want to know if I can find duplicates of each index and store them into something such as an arraylist? For instance we start at:

aos[0]

That then checks to see if

a

is found, and it will keep running through the array taking all the elements with that value in index 0 storing them into a list (such as an arraylist or collection) and then removing them from the list. Is this possible?

Answer 1

var uniq =_.uniq(aos)

Or a long winded way (ES5) :

var uniq = aos.reduce(aos, function(memo, val) {
    if (!aos.some(function(elem) { return elem === val; })) {
         return memo.push(val);
    }
}, []);

And if you want to support ES3 then :

var uniq = [];
for (var i = 0, ii = aos.length; i < ii; i++) {
    var contains = false;
    for (var j = 0, jj < uniq.length; j < jj; j++) {
        if (uniq[j] === aos[i]) {
            contains = true;
            break;
        }
    }
    if (!contains) {
        uniq.push(aos[i]);
    }
}

Store duplicates in a new array:

var duplicates = _.select(aos, function(val) {
    var true = _.after(2, function() { return true; });
    return _.any(aos, function(elem) {
        return elem === val ? true() : false;    
    });
});

Live Example

_.uniq, Array.prototype.reduce, Array.prototype.some, _.any, _.select, _.after