# combine

Learn how to combine two sets of values.

This method chains a `combine` operation to the patch, which combines two sets of values without duplicates.

Non-existent paths and null values are treated as an empty collection.

> **Atomicity**
>
> If the value at the specified path is not a collection, the operation fails and the entire patch is discarded.

## Signature

This method has the following signature:

```ts
patch.combine(path: string, value: JsonValue): Patch
```

The return is the `Patch` instance itself to allow operation chaining.

## Example

Here is a basic example of how to use this method:

```ts
path.combine('interests', 'data science');
```

The following table shows how the operation behaves in different scenarios:

| Current value | Given value   | Result       |
| ------------- | ------------- | ------------ |
| `[]`          | `[]`          | `[]`         |
| `[]`          | `['a', 'a']`  | `['a']`      |
| `['a']`       | `null`        | `['a']`      |
| `['a']`       | `'b'`         | `['a', 'b']` |
| `['a']`       | `['b', null]` | `['a', 'b']` |
| `[null]`      | `['a']`       | `['a']`      |
| `null`        | `null`        | `[]`         |
| `null`        | `['a']`       | `['a']`      |
| `null`        | `'a'`         | `['a']`      |
| `'a'`         | `'b'`         | `['a', 'b']` |
| `'a'`         | `['b']`       | `['a', 'b']` |
| `'a'`         | `['a']`       | `['a']`      |

## Parameters

The following list describes the supported parameters:

- `path`: `string`

  The path to the collection in dot notation, like `interests`.

- `value`: `JSON`

  The value to combine with the Current value, like `data science`.