uniqueArray = a.filter(function(item, pos) {
    return a.indexOf(item) == pos;
})

function uniq(a) {
    var seen = {};
    return a.filter(function(item) {
        return seen.hasOwnProperty(item) ? false : (seen[item] = true);
    });
}

function uniq(a) {
    var prims = {"boolean":{}, "number":{}, "string":{}}, objs = [];

    return a.filter(function(item) {
        var type = typeof item;
        if(type in prims)
            return prims[type].hasOwnProperty(item) ? false : (prims[type][item] = true);
        else
            return objs.indexOf(item) >= 0 ? false : objs.push(item);
    });
}

function uniq_fast(a) {
    var seen = {};
    var out = [];
    var len = a.length;
    var j = 0;
    for(var i = 0; i < len; i++) {
         var item = a[i];
         if(seen[item] !== 1) {
               seen[item] = 1;
               out[j++] = item;
         }
    }
    return out;
}

uniqArray = a.filter( (item, pos, arr) => !pos || item !== arr[pos - 1] );

function doSmth(a) {
  for (var q=1, i=1; q<a.length; ++q) {
    if (a[q] !== a[q-1]) {
      a[i++] = a[q];
    }
  }

  a.length = i;
  return a;
}