There are many ways to accomplish your goal, depending on how you want to use the data. If the arrays are always the same length, essentially what you need to do is create a new array of objects, checking to see if the product_id and product_category_id combination have already been added. If they have, you add the product amount to that entry, and if not, you create a new entry to the data.

Once the data is organized in an array, you can do anything you want with it. I filled a table out with the data as a simple demo.

hopefully this points you in the right direction 👍 if you have any questions about my code, please ask.

const product_id = [4,5,1,3,5];
const product_category_id = [2,2,1,3,2];
const product_amount = [3000,4000,5000,5000,4000];
const productData = [];
//format data
for (let i = 0; i < product_id.length;  i++) {
  const pid = product_id[i];
  const pcid = product_category_id[i];
  const prodAmt = product_amount[i];
  const target = productData.find(data => data.pid == pid && data.pcid == pcid);
  if (target) target.prodAmt += prodAmt;
  else productData.push({pid, pcid, prodAmt});
}
//create rows
const table = document.querySelector("table");
for (const data of productData) {
  const tr = document.createElement("tr");
  const values = Object.values(data);
  for (const value of values) {
    const td = document.createElement("td");
    td.innerText = value;
    tr.appendChild(td);
  }
  table.appendChild(tr);
}

<table>
  <tr>
    <th>product_id</th>
    <th>product_category_id</th>
    <th>product_new_amount</th>
  </tr>
</table>

This solution can help you. Please, try this:

const product_id = [4,5,1,3,5];
const product_category_id =[2,2,1,3,2];
const product_amount =[3000,4000,5000,5000,4000];

function find_duplicate_in_array(array){
const count = {}; const category_id = {}; const amount = {};
const result = [];

array.forEach((item,index) => {
    if (count[item]) {
       count[item] +=1;
       amount[item] += product_amount[index];
       return
    }
    count[item] = 1; 
    amount[item] = product_amount[index];
    category_id[item] = product_category_id[index];
});

for(let prop in count){
    result.push({product_id:prop,product_category_id:category_id[prop],product_new_amount:amount[prop]})
}

console.log('result---->', result);
return result;
}
find_duplicate_in_array(product_id);

First, make objects out of your arrays.

product_id = [4,5,1,3,5];
product_category_id =[2,2,1,3,2];
product_amount =[3000,4000,5000,5000,4000];

function Item(i,ci,a) {
this.id=i;
this.category_id=ci;
this.amount=a;
}

obj=[];
product_id.forEach((v,k)=>{obj.push(new Item(product_id[k],product_category_id[k],product_amount[k]))});
document.write(JSON.stringify(obj),'<br>');

document.write('<br>');

Then create two Map's, one for the id:amount pairing, and the other for the id:category relation.

Run through the amounts, and if the key already exists, add the new value to it. If not, update both Map's with the new key and respective value.

m=new Map(); m2=new Map();
obj.forEach(o=>{
if (m.has(o.id)) m.set(o.id,m.get(o.id)+o.amount);
else {
m.set(o.id,o.amount);
m2.set(o.id,o.category_id);
}
});

Finally, display the data, taking care to use the correct Map.

m.forEach((v,k)=>document.write(k+', '+m2.get(k)+', '+v,'<br>'));

Put it together:

product_id = [4,5,1,3,5];
product_category_id =[2,2,1,3,2];
product_amount =[3000,4000,5000,5000,4000];

function Item(i,ci,a) {
this.id=i;
this.category_id=ci;
this.amount=a;
}

obj=[];
product_id.forEach((v,k)=>{obj.push(new Item(product_id[k],product_category_id[k],product_amount[k]))});
document.write(JSON.stringify(obj),'<br>');

document.write('<br>');

m=new Map(); m2=new Map();
obj.forEach(o=>{
if (m.has(o.id)) m.set(o.id,m.get(o.id)+o.amount);
else {
m.set(o.id,o.amount);
m2.set(o.id,o.category_id);
}
});

m.forEach((v,k)=>document.write(k+', '+m2.get(k)+', '+v,'<br>'));