@stdlib/utils/find/README.md

Standard utilities.

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# Find

> Find elements in an array-like object that satisfy a test condition.

<section class="usage">

## Usage

<!-- eslint-disable stdlib/no-redeclare -->

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

#### find( arr, \[opts,] clbk )

Finds elements in an array-like object that satisfy a test condition. The function accepts two options: `k` and `returns`.

-   **k**: an `integer` which limits the number of elements returned and whose sign determines the direction in which to search. If set to a negative `integer`, the function searches from the last element to the first element.

-   **returns**: specifies the type of result to return and may be one of three options: `indices`, `values`, `*`.

    -   **indices**: indicates to return the element indices of those elements satisfying the search condition.
    -   **values**: indicates to return the element values of those elements satisfying the search condition.
    -   **\***: indicates to return both the element indices and values of those elements satisfying the search condition. The returned result is an `array` of `arrays`, where each sub-array is an index-value pair.

The `callback` is provided three arguments:

-   **element**: the current element
-   **index**: the current element's index
-   **array**: the input `array`, `typed array` or `string`

By default, `k` is the length of `arr` and `returns` is set to `indices`.

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

function greaterThan20( val ) {
    return val > 20;
}

var vals = find( data, greaterThan20 );
// returns [ 0, 2, 3 ]

data = 'Hello World';
function isUpperCase( val ) {
    return /[A-Z]/.test( val );
}

vals = find( data, isUpperCase );
// returns [ 0, 6 ]
```

To limit the number of results and specify that `values` should be returned,

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': 2,
    'returns': 'values'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 30, 50 ]
```

If no `array` elements satisfy the test condition, the function returns an empty `array`.

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': 2,
    'returns': 'values'
};

function condition( val ) {
    return val > 1000;
}

var vals = find( data, opts, condition );
// returns []
```

To find the last two values satisfying a search condition,

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': 'values'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 60, 50 ]
```

To explicitly specify that only indices are returned,

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': 'indices'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 3, 2 ]
```

And to return both indices and values as index-value pairs,

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': '*'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ [3, 60], [2, 50] ]
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint-disable stdlib/no-redeclare -->

<!-- eslint no-undef: "error" -->

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

// Simulate the data...
var data = new Array( 100 );
var i;
for ( i = 0; i < data.length; i++ ) {
    data[ i ] = round( randu*100 );
}

// Find the first 10 values greater than 25...
var opts = {
    'k': 10,
    'returns': '*'
};

function condition( val ) {
    return val > 25;
}

var vals = find( data, opts, condition );
console.log( vals.join( '\n' ) );
```

</section>

<!-- /.examples -->

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</section>

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