rmdups.js

var items_2 = [];
var weights_2 = [];

for (var i = items.length - 1; i > 0; i++) {
    if (i == items.indexOf(items[i])) { // If not a duplicate
        items_2.push(items[i]);
        weights_2.push(weights[i]);
    }
}

items = items_2; // items_2 now contains all unique items
weights = weights_2; // weights_2 now contains the weights of all unique items

// This will be O(n^2), with a more complicated system with Maps or Sets you could probably get O(nlogn)