shopify:cart:discount-update

Fires when a buyer applies or removes a discount code.

You can use this to see which codes buyers try, or to react when a code your app owns is applied.

discountCodes is the complete set the cart should end up with, not a delta, so send every code the buyer should have and send an empty array to clear them all. The resolved cart reports which of them the cart accepted.

You dispatch it from the discount form, when the buyer submits and before the result is known. A code the cart won't apply still resolves the promise, and the matching discountCodes entry comes back with applicable: false. A failed request rejects the promise and dispatches shopify:cart:error.

Anchor to propertiesProperties

Anchor to discountCodes discountCodes [] required: The full set of codes the cart should end up with. This replaces the existing codes rather than adding to them, so send an empty array to clear them all.
Anchor to promise promise Promise<> required: Resolves with a CartDiscountUpdateResult when the update finishes. It rejects if the request fails or is aborted.
Anchor to detail detail Record<string, unknown>: Optional custom data for the storefront's internal use. Listeners can read it.

DiscountCode

A discount code applied to the cart.

code
The code as the buyer typed it, such as `SPRING20`.
```
string
```

CartDiscountUpdateResult

The value a `shopify:cart:discount-update` promise resolves with.

cart
The cart after the codes were applied. Check `discountCodes[].applicable` to see which ones the cart accepted.
```
StandardEventCart | null
```
userErrors
Validation errors from the mutation.
```
CartMutationUserError[]
```
warnings
Non-blocking warnings from the mutation.
```
CartMutationWarning[]
```
detail
Optional custom data for the storefront's internal use. Listeners can read it.
```
Record<string, unknown>
```

StandardEventCart

A subset of the [Storefront API Cart object](/docs/api/storefront/latest/objects/Cart) that cart events carry.

id
The cart GID.
```
string
```
totalQuantity
The total number of items in the cart.
```
number
```
cost
The total cost of the cart.
```
StandardEventCartCost
```
lines
The lines in the cart.
```
StandardEventCartLine[]
```
discountCodes
The discount codes on the cart.
```
StandardEventCartDiscountCode[]
```

StandardEventCartCost

The cost of a cart or a cart line.

totalAmount
The total amount.
```
MoneyV2
```

MoneyV2

An amount with its currency, matching the Storefront API [`MoneyV2`](/docs/api/storefront/latest/objects/MoneyV2) format.

amount
A decimal money amount, such as `29.99`.
```
string
```
currencyCode
The three-letter currency code, such as `USD`.
```
string
```

StandardEventCartLine

A single line in the cart.

id
The cart line ID. A storefront on the AJAX cart API passes its own line keys through, so don't assume a GID.
```
string
```
quantity
The quantity of merchandise on the line.
```
number
```
cost
The cost of the line.
```
StandardEventCartCost
```

StandardEventCartDiscountCode

A discount code on the cart.

code
The discount code the buyer entered.
```
string
```
applicable
Whether the discount code applies to the cart.
```
boolean
```

CartMutationUserError

A validation error returned by a cart mutation.

code
A machine-readable error code, such as `INVALID` for a malformed input or `MAXIMUM_EXCEEDED` for a quantity above the item's maximum. See [`CartErrorCode`](/docs/api/storefront/latest/enums/CartErrorCode) for the full list.
```
string
```
field
The path to the field that caused the error.
```
string[]
```
message
A human-readable message.
```
string
```

CartMutationWarning

A non-blocking warning returned by a cart mutation.

code
A machine-readable warning code, such as `MERCHANDISE_OUT_OF_STOCK` for a line whose merchandise ran out or `MERCHANDISE_NOT_ENOUGH_STOCK` when only part of the requested quantity is available. See [`CartWarningCode`](/docs/api/storefront/latest/enums/CartWarningCode) for the full list.
```
string
```
message
A human-readable message.
```
string
```
target
The cart line or field the warning applies to.
```
string
```

Examples

Dispatch the event

import { CartDiscountUpdateEvent } from '@shopify/standard-events';

const deferred = CartDiscountUpdateEvent.createPromise();

element.dispatchEvent(

new CartDiscountUpdateEvent({

discountCodes: [{ code: 'SPRING20' }],

promise: deferred.promise,

}),

);

const ajaxCart = await applyDiscounts(['SPRING20']);

deferred.resolve({

cart: CartDiscountUpdateEvent.createCartFromAjaxResponse(ajaxCart),

});

Examples

Dispatch the event

import { CartDiscountUpdateEvent } from '@shopify/standard-events';

const deferred = CartDiscountUpdateEvent.createPromise();

element.dispatchEvent(
  new CartDiscountUpdateEvent({
    discountCodes: [{ code: 'SPRING20' }],
    promise: deferred.promise,
  }),
);

const ajaxCart = await applyDiscounts(['SPRING20']);

deferred.resolve({
  cart: CartDiscountUpdateEvent.createCartFromAjaxResponse(ajaxCart),
});

Listen for the event

document.addEventListener('shopify:cart:discount-update', (event) => {
  event.promise.then(({ cart }) => {
    const rejected = cart?.discountCodes.filter((code) => !code.applicable);

    if (rejected?.length) {
      showMessage(`${rejected[0].code} isn't valid for this cart.`);
    }
  });
});

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