# Set

The `Set` object stores unique values of any type, whether primitive values or object references. The Set is used as storage for all multi-value objects in this API: custom fields that store multiple values, issue links, issues in a project, and so on. You can access single values in the collection directly (see `first()`, `last()`, `get(index)`), use an iterator (see `entries()`, `values()`), or traverse with `forEach(visitor)` and `find(predicate)` methods. The workflow API is based on ECMAScript 5.1. This Set implementation mimics the functionality supported by the [ES 6 Set interface](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set).

## Properties

| Name | Type | Description |
| --- | --- | --- |
| added |  [Set]()  |  The elements that are added to a field that stores multiple values in the current transaction. Only relevant when the Set represents a multi-valued property (field) of a persistent entity.   |
| isChanged |  boolean  |  When the Set represents a multi-valued property (field) of a persistent entity and the field is changed in the current transaction, this property is `true`.   |
| removed |  [Set]()  |  The elements that are removed from a field that stores multiple values in the current transaction. Only relevant when the Set represents a multi-valued property (field) of a persistent entity.   |
| size |  number  |  The number of elements in a Set. Use thoughtfully, as the calculation for large collections (like `project.issues`) may be resource consumptive.   |

## Methods

### add

```JAVASCRIPT
add(element)
```

Add an element to a Set. If the specified value is already present, a duplicate value is not added.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | element |  Object  |  The element to add to the Set.                     |

### clear

```JAVASCRIPT
clear()
```

Remove all of the values from a Set.

### delete

```JAVASCRIPT
delete(element)
```

Remove an element from a Set. If the specified element is not present, nothing happens.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | element |  Object  |  The element to remove from the Set.                     |

### entries

```JAVASCRIPT
entries()
```

Get an iterator for the entries in a Set. The same as `values()`. Use an iterator when you need to traverse over entries until a specific condition is met and modify the entries at the same time.

Return Value
: | Type | Description |
: | --- | --- |
: |  [Iterator](v1-Iterator.html).<Object>  |  An iterator for the collection of values.                 |

Example
: ```JAVASCRIPT
: // We want to find first Critical among issue subtasks and assign it.
: const checkAndAssign = function(task) {
: if (task.fields.Priority.name === ctx.Priority.Critical.name) {
: task.fields.Assignee = ctx.currentUser;
: return true;
: }
: return false;
: };
: const iter = issue.links['parent for'].entries();
: let v = iter.next();
: while (!v.done && !checkAndAssign(v.value)) {
: v = iter.next();
: }
: ```

See Also
: * If you need to modify all of the elements in the Set, see `forEach(visitor)`.
:
: * If you need to find an element that meets specific criteria, see `find(predicate)`.

### find

```JAVASCRIPT
find(predicate)
```

Find the first element in a Set for which a predicate function returns `true`.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | predicate |  function  |  A function with one argument that returns either `true` or `false` for a given value in the Set.                     |

Return Value
: | Type | Description |
: | --- | --- |
: |  Object  |  The first value that returns `true` for the predicate function or undefined.                 |

Example
: ```JAVASCRIPT
: issue.tags.find(function(tag) {
: return tag.name === 'release';
: });
: ```

### first

```JAVASCRIPT
first()
```

Find the first object in a collection based on the order in which the elements were added to the Set.

Return Value
: | Type | Description |
: | --- | --- |
: |  Object  |  The first object in a collection or `null` if the collection is empty.                 |

### forEach

```JAVASCRIPT
forEach(visitor)
```

Apply a visitor function to each member of a collection.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | visitor |  function  |  The function to be applied to each member of the collection.                     |

Example
: ```JAVASCRIPT
: issue.links['parent for'].forEach(function(child) {
: child.fields.Priority = issue.fields.Priority;
: });
: ```

### get

```JAVASCRIPT
get(index)
```

Find an element with a specific index position in a Set.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | index |  number  |  The ordinal index of the element to be returned from the Set.                     |

Return Value
: | Type | Description |
: | --- | --- |
: |  Object  |  An object at index position in a Set, or `null` if the Set contains fewer than (index + 1) elements.                 |

### has

```JAVASCRIPT
has(element)
```

Checks a Set object to determine whether the specified element is present in the collection or not.

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | element |  Object  |  The element to locate in the Set.                     |

Return Value
: | Type | Description |
: | --- | --- |
: |  boolean  |  If the element is found, returns `true`, otherwise, `false`.                 |

### isEmpty

```JAVASCRIPT
isEmpty()
```

Checks a Set object to determine whether it is empty.

Return Value
: | Type | Description |
: | --- | --- |
: |  boolean  |  If the Set is empty, returns `true`, otherwise, `false`.                 |

### isNotEmpty

```JAVASCRIPT
isNotEmpty()
```

Checks a Set object to determine whether it is not empty.

Return Value
: | Type | Description |
: | --- | --- |
: |  boolean  |  If the Set is not empty, returns `true`, otherwise, `false`.                 |

### last

```JAVASCRIPT
last()
```

Find the last object in a collection based on the order in which the elements were added to the Set.

Return Value
: | Type | Description |
: | --- | --- |
: |  Object  |  The last object in a collection or `null` if collection is empty.                 |

### map

```JAVASCRIPT
map(visitor)
```

Transform each element in a Set and return the results as an array.

Available since 2025.3

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | visitor |  function  |  A function called for each value with arguments `(value, index, set)`.                     |

Return Value
: | Type | Description |
: | --- | --- |
: |  Array.<*>  |  An array with the results of calling `visitor` on each element in insertion order.                 |

Example
: ```JAVASCRIPT
: // Collect logins of all permitted users
: const logins = issue.permittedUsers.map((u) => u.login);
: ```

### slice

```JAVASCRIPT
slice(start, end)
```

Create a shallow copy of a portion of a Set as an array.

Available since 2025.3

Parameters
: | Name | Type | Description |
: | --- | --- | --- |
: | start |  number  |  Zero-based index at which to begin extraction. Negative values are treated as 0.                     |
: | end |  number  |  Zero-based index before which to end extraction. If omitted, extracts through the end.                     |

Return Value
: | Type | Description |
: | --- | --- |
: |  Array.<Object>  |  An array containing the extracted values in insertion order. Returns an empty array when the range is empty.                 |

Example
: ```JAVASCRIPT
: // Get first 3 subtasks
: const firstThree = issue.links['parent for'].slice(0, 3);
: ```

### values

```JAVASCRIPT
values()
```

Get an iterator for the entries in a Set. The same as `entries()`.

Return Value
: | Type | Description |
: | --- | --- |
: |  [Iterator](v1-Iterator.html).<Object>  |  An iterator for the collection of values.                 |

See Also
: * For details, see `entries()`.

## See also

[Iterator](v1-Iterator.html)