How to correctly write values ​​to localStorage?

Question

PHP

There is a page that contains a product and an "add to cart" button. When the button is clicked, the product ID (taken from the database) is written to localStorage. The problem is that I don't understand how to correctly implement key to write value to it (which corresponds to the product ID). In the JS file, I've marked the keyName as 'products'. And now, when adding a value, it is permanently assigned the products key. Those. I add, for example, a product with ID = 1. I get "products" in lS with the value "1". I add a product with ID = 2, the value "products" in lS is overwritten from "1" to "2", etc.

Here is the code from the product page:

<h1><i><?=Html::encode($product->product_name)?></i></h1>
<p><img src="https://i.blogs.es/96715c/screenshot_5596/450_1000.jpeg" alt="Sony PlayStation 5" style="width:350px; height:290px" class="leftimg"></p>

<fieldset>
    <legend><b> Описание продукта </b></legend>
    <p><?=Html::encode($product->info)?></p>
</fieldset>

<button class="k"><a class="product_link_id" data-id="<?php echo $product->ID?>">Купить</a></button>
/*
<script>
    const btn = document.querySelector('.k > a');
    btn.addEventListener('click', function () {
        btn.innerHTML = 'Уже в корзине'
    });
</script>
*/
<?=Html::encode($product->product_price)?> рублей.

And here is the JS code for adding a product to localStorage:

let count = {

};

this.keyName = 'products';

// Получаю ID'шник кнопки.
document.querySelector('.product_link_id').onclick = () => {
    getItemId(event.target.dataset.id);
};

// Убираю object Object из localStorage
localStorage.setItem(this.keyName, JSON.stringify(count));
const di = localStorage.getItem(this.keyName);
id = JSON.parse(di);

// Добавление товара в корзину
const getItemId = id => {
    count[id]++;
    console.log(localStorage.setItem(this.keyName, id));
};

As I understand it, this is due to the fact that my 'keyName' is just statistically scored as 'products'. But here's how to do it differently, I'm not really fumbling.

Answer 1

localStorage.setItem(this.keyName, JSON.stringify(count));
const di = localStorage.getItem(this.keyName);
id = JSON.parse(di);

do you understand what your code is doing?