Need help running a loop through an array (object)

How do I run a simple loop through an object array that will check for similarities of a previously exctracted value from a form. I am doing a project in which I am setting up a pizzeria. The user will input desired size of pizza and toppings in a form. I will then extract the values for total.

This is the JavaScript code I used to extract the values from the form:

let form=document.querySelector("form");
form.addEventListener("submit",(event)=>{
event.preventDefault();
// run an array through the checkbox
let topping=[];
document.querySelectorAll('[type="checkbox"]').forEach(item=>{
if (item.checked=== true)
{
topping.push(item.value);
}})


//to extract the value of the text field:
let fullname=document.querySelector("#fullname").value;
let address=document.querySelector("#address").value;
let pies=document.querySelector("#pies").value;
let pizzasize=document.querySelector('input[name="size"]:checked').value;