# Building basic JOLT transformations JOLT can be used for diverse types of transformations, from basic to advanced. In this document, we will introduce you to the **basic operations**, that allows you to: * Restructure the JSON or rename fields. * Insert default values if fields are missing. * Delete specific fields. * Arrange fields in alphabetical order. {% hint style="success" %} **Tip:** Test the examples from this document in the [JOLT playground](https://jolt-demo.appspot.com/#inception). {% endhint %} ## **Understanding the basic JOLT operations** In this section, you’ll learn how each basic JOLT operation works (`shift`, `default`, `remove`, and `sort)` and when to use them. ### **shift** The `shift` operation restructures a JSON object by remapping its fields, without modifying their values. It works by specifying **where to extract values from** in the original JSON and **where to place them** in the new structure. #### **Practical example** * **Use case:** Transforming a product catalog to match a new format. * **Goal:** Group product details under a `details` object and rename fields. **Input JSON** {% code expandable="true" %} ```json { "product": { "id": "12345", "name": "Smartphone X1", "brand": "TechBrand", "price": 699.99, "currency": "USD", "stock": 25 } } ``` {% endcode %} **Desired output JSON** {% code expandable="true" %} ```json { "productId": "12345", "details": { "name": "Smartphone X1", "brand": "TechBrand", "pricing": { "amount": 699.99, "currency": "USD" }, "availability": 25 } } ``` {% endcode %} **Transformation spec** {% code expandable="true" %} ```json [ { "operation": "shift", "spec": { "product": { "id": "productId", "name": "details.name", "brand": "details.brand", "price": "details.pricing.amount", "currency": "details.pricing.currency", "stock": "details.availability" } } } ] ``` {% endcode %} **Explanation** * `"id": "productId"` moves the `product.id` to the top level with a new key. * `"name"` and `"brand"` are grouped under `details`. * `"price"` and `"currency"` are nested under `details.pricing` to organize pricing information. * `"stock"` is renamed to `availability` and grouped under `details`. Using **dot notation** (`.`) and hierarchical paths in the spec, you can organize complex output structures with minimal effort. {% hint style="warning" %} Only the fields explicitly mapped in the transformation spec will appear in the output. Any other data from the input is ignored. {% endhint %} ### **default** The `default` operation adds fields to a JSON object **when they don’t already exist**. It’s useful for populating missing data with predefined values. #### **Practical example** * **Use case:** Completing customer data with a default birth date. * **Goal:** Ensure that the output JSON includes the `birthDate` field, even if it’s missing in the output. **Input JSON** ```json { "customer": { "name": "Customer Default", "ssn": "123-45-6789" } } ``` **Desired output JSON** ```json { "customer": { "name": "Customer Default", "ssn": "123-45-6789", "birthDate": "01/01/1970" } } ``` **Transformation spec** {% code expandable="true" %} ```json [ { "operation": "default", "spec": { "customer": { "birthDate": "01/01/1970" } } } ] ``` {% endcode %} **Explanation** * The `default` operation checks whether the field `customer.birthDate` exists. * If it’s missing, the value `"01/01/1970"` is added as a default. * If the field already exists, its original value is preserved. This operation is useful when you want to ensure that specific fields are present in the output, even if they’re not provided in the input. {% hint style="warning" %} The `default` operation does **not** overwrite existing values, it only fills missing values. {% endhint %} ### **remove** The `remove` operation **deletes specific fields or objects** from a JSON structure. You must navigate to the field you want to remove and assign it an empty string (`“ ”`) in the spec. #### **Practical example** * **Use case:** Cleaning up customer data by removing unnecessary fields. * **Goal:** Exclude the `birthDate` field from the customer object. **Input JSON** ```json { "customer": { "name": "Customer Default", "ssn": "123.456.789.10", "birthDate": "01/01/1970" } } ``` **Desired output JSON** ```json { "customer": { "name": "Customer Default", "ssn": "123.456.789.10" } } ``` **Transformation spec** {% code expandable="true" %} ```json [ { "operation": "remove", "spec": { "customer": { "birthDate": "" } } } ] ``` {% endcode %} **Explanation** * The transformation navigates to `customer.birthDate` and removes it by assigning `""` (an empty string). * Only fields explicitly assigned to an empty string will be removed. * Any incorrect or non-empty assignment will cause the operation to fail. {% hint style="warning" %} Make sure to use an empty string (`" "`) to indicate that the field should be removed. This is required for the operation to succeed. {% endhint %} ### **sort** The `sort` operation **organizes all fields and objects in a JSON in alphabetical order** by key name. It applies globally. The sort order can’t be customized, and **only the keys are sorted**, not the values. #### **Practical example** * **Use case:** Alphabetizing employee data fields for consistency. * **Goal:** Ensure all fields in the output appear in alphabetical order. **Input JSON** ```json { "employee": { "phone": "9 9999-9999", "name": "Employee Sort", "birthDate": "01/01/1980", "role": "JOLT Analyst" } } ``` **Desired output JSON** ```json { "employee": { "birthDate": "01/01/1980", "name": "Employee Sort", "phone": "9 9999-9999", "role": "JOLT Analyst" } } ``` **Transformation spec** ```json [ { "operation": "sort" } ] ``` **Explanation** * No `spec` is needed for the `sort` operation. Only the operation must be declared. * All object fields in the JSON are sorted alphabetically by key name. * Sorting applies recursively to nested objects as well. ## **Continue learning** Now that you’ve covered the essentials, you can move on to the next topics: * [**JOLT operators**](https://docs.digibee.com/documentation/resources/use-cases/how-to-jolt/operators), key elements that make your specifications more dynamic and flexible. * [**Advanced operations**](https://docs.digibee.com/documentation/resources/use-cases/how-to-jolt/advanced-operations), where you’ll explore more sophisticated transformation techniques. * [**Use case examples**](https://docs.digibee.com/documentation/resources/use-cases/how-to-jolt/use-cases), demonstrating how JOLT works in real integration scenarios.