# Adding Transaction Lines

### Data Addition Methods

#### Add Lines to an Existing Transaction Cart

* **Description:** Adds one or more lines to an existing transaction cart using the addLines function, requiring a transaction UUID and line details. The leadingLine parameter is optional, used for bonus items linked to a parent item.
* **Namespace:** Currently implemented only for the "app" namespace.
* **Behavior:** Applies only to the cart, not the Order Center.
* **Syntax:**

  ```javascript
  pepperi.app.transactions.addLines({
    transaction: { UUID: "<transaction UUID>" },
    lines: [
      {
        item: { ExternalID: "<externalID>" },
        lineData: { <field1>: <value1>, <field2>: <value2> },
        leadingLine: { UUID: "<leadingLine UUID>" } // Optional
      }
    ]
  });
  ```
* **Example:**

  ```javascript
  pepperi.app.transactions.addLines({
    transaction: { UUID: "11cda91f-df09-4d3c-826d-184e5f394d06" },
    lines: [
      {
        item: { ExternalID: "MCR00101BLUEL" },
        lineData: { UnitsQuantity: 5 },
        leadingLine: { UUID: "11cda91f-df09-4d3c-826d-184e5f394d0d" }
      }
    ]
  });
  ```
* **Returns:**

  ```json
  {
    "success": true,
    "result": [
      {
        "id": "69dc3368-c74a-4616-b1dc-b21ba38c4daa",
        "status": "added",
        "message": ""
      }
    ]
  }
  ```