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# anyBy

> Test whether at least one element in an array passes a test implemented by a predicate function.

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## Usage

```javascript
var anyBy = require( '@stdlib/array/base/any-by' );
```

#### anyBy( x, predicate\[, thisArg] )

Tests whether at least one element in an array passes a test implemented by a `predicate` function.

```javascript
function isPositive( value ) {
    return ( value > 0 );
}

var x = [ 0, 0, 1, 0 ];

var bool = anyBy( x, isPositive );
// returns true
```

If a `predicate` function returns a truthy value, the function **immediately** returns `false`.

```javascript
function isPositive( value ) {
    return ( value > 0 );
}

var x = [ -1, -2, -3, -4 ];

var bool = anyBy( x, isPositive );
// returns false
```

The `predicate` function is provided three arguments:

-   **value**: current array element.
-   **index**: current array element index.
-   **arr**: input array.

To set the `predicate` function execution context, provide a `thisArg`.

```javascript
function predicate( value ) {
    this.count += 1;
    return ( value > 0 );
}

var x = [ -1, -2, 3, -4 ];

var context = {
    'count': 0
};

var bool = anyBy( x, predicate, context );
// returns true

var cnt = context.count;
// returns 3
```

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## Notes

-   If provided an array-like object having a `some` method (**as defined by the ECMAScript Standard**), the function defers execution to that method and assumes that the method API has the following signature:

    ```text
    x.some( predicate, thisArg )
    ```

-   If provided an array-like object without a `some` method, the function performs a linear scan and returns immediately upon encountering a truthy return value. Unlike [`Array.prototype.some`][mdn-array-some], when performing a linear scan, the function does **not** skip `undefined` elements.

-   If provided an empty array, the function returns `false`.

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## Examples

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

```javascript
var bernoulli = require( '@stdlib/random/array/bernoulli' );
var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
var naryFunction = require( '@stdlib/utils/nary-function' );
var anyBy = require( '@stdlib/array/base/any-by' );

var x = bernoulli( 10, 0.1, {
    'dtype': 'int8'
});
// returns <Int8Array>

var out = anyBy( x, naryFunction( isPositiveInteger, 1 ) );
// returns <boolean>
```

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

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