Custom attributes can contain hyphens in their names, like this:
<div id="elem" data-my-test="1000"></div>
To refer to such attributes, use camelCase:
let elem = document.querySelector('#elem'); console.log(elem.dataset.myTest);
Given the following code:
<div id="elem" data-product-price="1000" data-product-amount="5"> apples </div>
Make it so that when you click on the div, the purchase price is added to the end of its text, equal to the price multiplied by the quantity.