***

title: "OrderMergeStrategy"
generated: true
---------------

## OrderMergeStrategy

<GenerationInfo sourceFile="packages/core/src/config/order/order-merge-strategy.ts" sourceLine="48" packageName="@vendure/core" />

An OrderMergeStrategy defines what happens when a Customer with an existing Order
signs in with a guest Order, where both Orders may contain differing OrderLines.

Somehow these differing OrderLines need to be reconciled into a single collection
of OrderLines. The OrderMergeStrategy defines the rules governing this reconciliation.

:::info

This is configured via the `orderOptions.mergeStrategy` property of
your VendureConfig.

:::

```ts title="Signature"
interface OrderMergeStrategy extends InjectableStrategy {
    merge(ctx: RequestContext, guestOrder: Order, existingOrder: Order): MergedOrderLine[] | Promise<MergedOrderLine[]>;
}
```

* Extends: [`InjectableStrategy`](/current/core/reference/typescript-api/common/injectable-strategy#injectablestrategy)

<div className="members-wrapper">

### merge

\<MemberInfo kind="method" type={`(ctx: <a href='/current/core/reference/typescript-api/request/request-context#requestcontext'>RequestContext</a>, guestOrder: <a href='/current/core/reference/typescript-api/entities/order#order'>Order</a>, existingOrder: <a href='/current/core/reference/typescript-api/entities/order#order'>Order</a>) => <a href='/current/core/reference/typescript-api/orders/order-merge-strategy#mergedorderline'>MergedOrderLine</a>[] | Promise<<a href='/current/core/reference/typescript-api/orders/order-merge-strategy#mergedorderline'>MergedOrderLine</a>[]>`}   />

Merges the lines of the guest Order with those of the existing Order which is associated
with the active customer.

</div>
## MergedOrderLine

<GenerationInfo sourceFile="packages/core/src/config/order/order-merge-strategy.ts" sourceLine="15" packageName="@vendure/core" />

The result of the [OrderMergeStrategy](/current/core/reference/typescript-api/orders/order-merge-strategy#ordermergestrategy) `merge` method.

```ts title="Signature"
interface MergedOrderLine {
    orderLineId: ID;
    quantity: number;
    customFields?: any;
}
```

<div className="members-wrapper">

### orderLineId

\<MemberInfo kind="property" type={`<a href='/current/core/reference/typescript-api/common/id#id'>ID</a>`}   />

### quantity

\<MemberInfo kind="property" type={`number`}   />

### customFields

\<MemberInfo kind="property" type={`any`}   />

</div>