@stdlib/utils/bifurcate/README.md

Standard utilities.

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# bifurcate

> Split values into two groups.

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## Usage

```javascript
var bifurcate = require( '@stdlib/utils/bifurcate' );
```

#### bifurcate( collection, \[options,] filter )

Splits values into two groups. If an element in `filter` is truthy, the corresponding element in `collection` belongs to the first group; otherwise, the `collection` element belongs to the second group.

```javascript
var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var out = bifurcate( arr, filter );
// returns [ [ 'beep', 'boop', 'bar' ], [ 'foo' ] ]
```

The function accepts the following `options`:

-   **returns**: specifies the output format. If the option equals `'values'`, the function outputs element values. If the option equals `'indices'`, the function outputs element indices. If the option equals `'*'`, the function outputs both element indices and values. Default: `'values'`.

By default, the function returns element values. To return element indices, set the `returns` option to `'indices'`.

```javascript
var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var opts = {
    'returns': 'indices'
};
var out = bifurcate( arr, opts, filter );
// returns [ [ 0, 1, 3 ], [ 2 ] ]
```

To return index-element pairs, set the `returns` option to `'*'`.

```javascript
var arr = [ 'beep', 'boop', 'foo', 'bar' ];
var filter = [ true, true, false, true ];

var opts = {
    'returns': '*'
};
var out = bifurcate( arr, opts, filter );
// returns [ [ [ 0, 'beep' ], [ 1, 'boop' ], [ 3, 'bar' ] ], [ [ 2, 'foo' ] ] ]
```

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## Notes

-   Both `collection` and `filter` **must** be collections. A collection may be either an [`Array`][mdn-array], [`Typed Array`][mdn-typed-array], or an array-like [`Object`][mdn-object] (excluding `strings` and `functions`).

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## Examples

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```javascript
var randu = require( '@stdlib/random/base/randu' );
var floor = require( '@stdlib/math/base/special/floor' );
var bifurcate = require( '@stdlib/utils/bifurcate' );

var vals;
var arr;
var out;
var f;
var i;
var j;

vals = [ 'beep', 'boop', 'foo', 'bar', 'woot', 'woot' ];

// Generate a random collection...
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
    j = floor( randu()*vals.length );
    arr[ i ] = vals[ j ];
}

// Randomly assign collection values to a group...
f = new Array( arr.length );
for ( i = 0; i < arr.length; i++ ) {
    f[ i ] = ( randu() < 0.5 );
}

// Compute the groups:
out = bifurcate( arr, f );
console.log( out );
```

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* * *

## See Also

-   <span class="package-name">[`@stdlib/utils/bifurcate-by`][@stdlib/utils/bifurcate-by]</span><span class="delimiter">: </span><span class="description">split values into two groups according to a predicate function.</span>
-   <span class="package-name">[`@stdlib/utils/bifurcate-own`][@stdlib/utils/bifurcate-own]</span><span class="delimiter">: </span><span class="description">split an object's own property values into two groups according to a predicate function.</span>
-   <span class="package-name">[`@stdlib/utils/group`][@stdlib/utils/group]</span><span class="delimiter">: </span><span class="description">group values as arrays associated with distinct keys.</span>

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[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[mdn-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object

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[@stdlib/utils/bifurcate-by]: https://github.com/stdlib-js/utils/tree/main/bifurcate-by

[@stdlib/utils/bifurcate-own]: https://github.com/stdlib-js/utils/tree/main/bifurcate-own

[@stdlib/utils/group]: https://github.com/stdlib-js/utils/tree/main/group

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