how to merge duplicate value in array of object site 3astackoverflow com

1var myArray = [
2    {productId: 116605, productserialno: "324234"},
3    {productId: 106290, productserialno: "12121"},
4    {productId: 106290, productserialno: "12121"},
5    {productId: 106293, productserialno: "4324343"}
6];
7
8var grouped = myArray.reduce(function (obj, product) {
9    obj[product.productId] = obj[product.productId] || [];
10    obj[product.productId].push(product.productserialno);
11    return obj;
12}, {});
13
14var groups = Object.keys(grouped).map(function (key) {
15    return {product: key, productserialno: grouped[key]};
16});
17
18var pre = document.createElement("pre");
19pre.innerHTML = JSON.stringify(groups, null, 4);
20document.body.appendChild(pre);