How to debug Converting circular structure to JSON?

Question

JavaScript

At some point I got an error:

error text

default_modal.js:135 Uncaught TypeError: Converting circular structure to JSON
    at JSON.stringify (<anonymous>)
    at addToCart (default_modal.js:135)
    at HTMLAnchorElement.<anonymous> (default_modal.js:75)
    at HTMLAnchorElement.dispatch (jquery.js:4737)
    at HTMLAnchorElement.elemData.handle (jquery.js:4549)
addToCart	@	default_modal.js:135
(anonymous)	@	default_modal.js:75
dispatch	@	jquery.js:4737
elemData.handle	@	jquery.js:4549

while in the line default_modal.js:135

localStorage.setItem('order_items',JSON.stringify(cart));

here is the function code:

function addToCart(data) {
        var cart = getCartObject(),
            el_name = getCartElementName(data);
        if(typeof cart[el_name] != 'undefined'){
            cart[el_name].count++;
        }else{
            cart[el_name] = data;
            cart[el_name].count = 1;
        }
        localStorage.setItem('order_items',JSON.stringify(cart));
        refreshCart();
    return true;
}

function getCartObject(){
    var cart = {};
    if (isLocalStorage()) {
        if (typeof localStorage.order_items !== 'undefined') {
            cart = JSON.parse(localStorage.order_items);
        }else{
            localStorage.order_items = JSON.stringify(cart);
        }
    }
    return cart;
}

At what everything worked, while it was localStorage.setItem, cleared it, now it should be created, it is created in the same form as it was, but it throws an error. I’ve been sitting for an hour already, I don’t understand where this creature found cyclicity.

Answer 1

Something inside the data object passed to addToCart contains a reference to the cart (or itself), forming the so-called. circular dependency, like:

var data = {
  1: "foo",
…
  d: data
}

Check what's in your cart before you doJSON.stringify(cart)