Grab multiple properties of a JSON

I’m working with a large JSON file that looks like this:

    "name": "Superproduct",
    "description": "Enjoy this amazing product.",
    "brand": "ACME",
    "categories": [
      "Soccer Ball",
      "Beach Ball"
    "type": "Online product",
    "price": 50,
    "price_range": "50 - 100",
    "image": "someImageURL",
    "url": "SomeProductURL",
    "free_shipping": true,
    "popularity": 10000,
    "rating": 2,
    "objectID": "1234"

I am trying to access every object with the Ball category, so that I can add a discount to that specific item. I realized that every object can have multiple variations of the word Ball in the category array.

Is there a way I can target the word ball in the array, so that I can add that to an array and apply the discount to every product with said criteria?

This is what I have so far, but I’m not sure if this is the best way, or if there’s a better way to accomplish what I’m trying to do:

async function setDiscount() {

    let discountedRate = 0.5;
    .then(res => res.json())
    .then(data => {for (let i = 0; i < data.length; i++) {
        if (data[i].categories[i] == "Ball") {
            data[i].price -= (data[i].price * discountedRate);



P.S.: I’m a newbie.