Js-buy-sdk: Uncaught (in promise) TypeError: Cannot read property 'checkoutLineItemsAdd' of undefined

[tonysparks5000]

Why is this happening im doing everything the docs want me to do?!

var lineItemsToAdd = [{ variant_id: variant.id, quantity: 1 }];
var checkoutId = Cart.data.checkout.id;
Cart.data.client.checkout.addLineItems(checkoutId, lineItemsToAdd).then((checkout) => {
// Do something with the updated checkout
console.log('add to cart',checkout.lineItems); // Array with one additional line item
});

gets

Uncaught (in promise) TypeError: Cannot read property 'checkoutLineItemsAdd' of undefined

[mightym]

Double check the key for the Variant ID. In my case it was wrong. It has to be:

const lineItemsToAdd = [{'variantId': variant.id, quantity:1 }]

You also have variant_id instead of variantId

[wedelgaard]

I had the same issue. Passing shopifyId as the variants id seemed to do the trick. Not the variants id (exposed from graphQL in my scenario)

[pfanone]

what is the shopifyId that you are referring to? the product objects id?

[pfanone]

Update:
In my case all of the id's I was passing were correct, however the function couldn't handle that I was passing quantity as "1" and not 1
it was a type casting issue smh