> For the complete documentation index, see [llms.txt](https://boxlang.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://boxlang.ortusbooks.com/boxlang-language/reference/built-in-functions/array/arrayflatmap.md).

# ArrayFlatMap

Maps each element and flattens the result one level.

```
 values = [ 1, 2, 3 ];
 values.flatMap( ( value ) => [ value, value * 10 ] );
 // [ 1, 10, 2, 20, 3, 30 ]
 
```

## Method Signature

```
ArrayFlatMap(array=[array], callback=[function:Function], parallel=[boolean], maxThreads=[any], virtual=[boolean])
```

### Arguments

| Argument     | Type                | Required | Description                                                                                                                                                                                                                               | Default |
| ------------ | ------------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `array`      | `array`             | `true`   | The array to transform                                                                                                                                                                                                                    |         |
| `callback`   | `function:Function` | `true`   | <p>The function to invoke for each item. The function will be passed 3 arguments: the current item, and the<br>current index, and the original array. You can alternatively pass a Java Function which will only receive the 1st arg.</p> |         |
| `parallel`   | `boolean`           | `false`  | If true, the function will be invoked in parallel using multiple threads. Defaults to false.                                                                                                                                              | `false` |
| `maxThreads` | `any`               | `false`  | The maximum number of threads to use when parallel is true. If not provided the common thread pool will be used. If a boolean value is passed, it will be assigned as the virtual argument.                                               |         |
| `virtual`    | `boolean`           | `false`  | If true, the function will be invoked using virtual thread. Defaults to false. Ignored if parallel is false.                                                                                                                              | `false` |

## Examples

### Transform each element and flatten the result one level

Each callback result is expected to be an array, and all results are flattened into a single array.

```java
values = [ 1, 2, 3 ];
result = values.flatMap( ( v ) => [ v, v * 10 ] );
writeOutput( result.toString() );

```

Result: \[1, 10, 2, 20, 3, 30]

### Expand a list of orders into individual items

```java
orders = [
    { id: 1, items: [ "apple", "banana" ] },
    { id: 2, items: [ "cherry" ] }
];
allItems = orders.flatMap( ( order ) => order.items );
writeOutput( allItems.len() );

```

Result: 3

### Using the global function form

```java
result = arrayFlatMap( [ 1, 2 ], ( v ) => [ v, v + 1 ] );
writeOutput( result.toString() );

```

Result: \[1, 2, 2, 3]

## Related

* [ArrayAppend](/boxlang-language/reference/built-in-functions/array/arrayappend.md)
* [ArrayAvg](/boxlang-language/reference/built-in-functions/array/arrayavg.md)
* [ArrayChunk](/boxlang-language/reference/built-in-functions/array/arraychunk.md)
* [ArrayClear](/boxlang-language/reference/built-in-functions/array/arrayclear.md)
* [ArrayContains](/boxlang-language/reference/built-in-functions/array/arraycontains.md)
* [ArrayContainsNoCase](/boxlang-language/reference/built-in-functions/array/arraycontainsnocase.md)
* [ArrayDelete](/boxlang-language/reference/built-in-functions/array/arraydelete.md)
* [ArrayDeleteAt](/boxlang-language/reference/built-in-functions/array/arraydeleteat.md)
* [ArrayDeleteNoCase](/boxlang-language/reference/built-in-functions/array/arraydeletenocase.md)
* [ArrayEach](/boxlang-language/reference/built-in-functions/array/arrayeach.md)
* [ArrayEvery](/boxlang-language/reference/built-in-functions/array/arrayevery.md)
* [ArrayFilter](/boxlang-language/reference/built-in-functions/array/arrayfilter.md)
* [ArrayFind](/boxlang-language/reference/built-in-functions/array/arrayfind.md)
* [ArrayFindAll](/boxlang-language/reference/built-in-functions/array/arrayfindall.md)
* [ArrayFindAllNoCase](/boxlang-language/reference/built-in-functions/array/arrayfindallnocase.md)
* [ArrayFindFirst](/boxlang-language/reference/built-in-functions/array/arrayfindfirst.md)
* [ArrayFindNoCase](/boxlang-language/reference/built-in-functions/array/arrayfindnocase.md)
* [ArrayFirst](/boxlang-language/reference/built-in-functions/array/arrayfirst.md)
* [ArrayFlatten](/boxlang-language/reference/built-in-functions/array/arrayflatten.md)
* [ArrayGetMetadata](/boxlang-language/reference/built-in-functions/array/arraygetmetadata.md)
* [ArrayGroupBy](/boxlang-language/reference/built-in-functions/array/arraygroupby.md)
* [ArrayIndexExists](/boxlang-language/reference/built-in-functions/array/arrayindexexists.md)
* [ArrayInsertAt](/boxlang-language/reference/built-in-functions/array/arrayinsertat.md)
* [ArrayIsDefined](/boxlang-language/reference/built-in-functions/array/arrayisdefined.md)
* [ArrayLast](/boxlang-language/reference/built-in-functions/array/arraylast.md)
* [ArrayMap](/boxlang-language/reference/built-in-functions/array/arraymap.md)
* [ArrayMax](/boxlang-language/reference/built-in-functions/array/arraymax.md)
* [ArrayMedian](/boxlang-language/reference/built-in-functions/array/arraymedian.md)
* [ArrayMerge](/boxlang-language/reference/built-in-functions/array/arraymerge.md)
* [ArrayMid](/boxlang-language/reference/built-in-functions/array/arraymid.md)
* [ArrayMin](/boxlang-language/reference/built-in-functions/array/arraymin.md)
* [ArrayNew](/boxlang-language/reference/built-in-functions/array/arraynew.md)
* [ArrayNone](/boxlang-language/reference/built-in-functions/array/arraynone.md)
* [ArrayPop](/boxlang-language/reference/built-in-functions/array/arraypop.md)
* [ArrayPrepend](/boxlang-language/reference/built-in-functions/array/arrayprepend.md)
* [ArrayPush](/boxlang-language/reference/built-in-functions/array/arraypush.md)
* [ArrayRange](/boxlang-language/reference/built-in-functions/array/arrayrange.md)
* [ArrayReduce](/boxlang-language/reference/built-in-functions/array/arrayreduce.md)
* [ArrayReduceRight](/boxlang-language/reference/built-in-functions/array/arrayreduceright.md)
* [ArrayReject](/boxlang-language/reference/built-in-functions/array/arrayreject.md)
* [ArrayResize](/boxlang-language/reference/built-in-functions/array/arrayresize.md)
* [ArrayReverse](/boxlang-language/reference/built-in-functions/array/arrayreverse.md)
* [ArraySet](/boxlang-language/reference/built-in-functions/array/arrayset.md)
* [ArrayShift](/boxlang-language/reference/built-in-functions/array/arrayshift.md)
* [ArraySlice](/boxlang-language/reference/built-in-functions/array/arrayslice.md)
* [ArraySome](/boxlang-language/reference/built-in-functions/array/arraysome.md)
* [ArraySort](/boxlang-language/reference/built-in-functions/array/arraysort.md)
* [ArraySplice](/boxlang-language/reference/built-in-functions/array/arraysplice.md)
* [ArraySum](/boxlang-language/reference/built-in-functions/array/arraysum.md)
* [ArraySwap](/boxlang-language/reference/built-in-functions/array/arrayswap.md)
* [ArrayToList](/boxlang-language/reference/built-in-functions/array/arraytolist.md)
* [ArrayToStruct](/boxlang-language/reference/built-in-functions/array/arraytostruct.md)
* [ArrayTranspose](/boxlang-language/reference/built-in-functions/array/arraytranspose.md)
* [ArrayUnique](/boxlang-language/reference/built-in-functions/array/arrayunique.md)
* [ArrayUnshift](/boxlang-language/reference/built-in-functions/array/arrayunshift.md)
* [ArrayZip](/boxlang-language/reference/built-in-functions/array/arrayzip.md)


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