@stdlib/utils/some-own-by/README.md

Standard utilities.

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# someOwnBy

> Test whether an object contains at least `n` own properties which pass a test implemented by a predicate function.

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## Usage

```javascript
var someOwnBy = require( '@stdlib/utils/some-own-by' );
```

#### someOwnBy( obj, n, predicate\[, thisArg ] )

Tests whether an `object` contains at least `n` own properties which pass a test implemented by a `predicate` function.

```javascript
function isNegative( value ) {
    return ( value < 0 );
}

var obj = {
    'a': 1,
    'b': -2,
    'c': 3,
    'd': -1
};

var bool = someOwnBy( obj, 2, isNegative );
// returns true
```

Once the function finds `n` successful properties, the function **immediately** returns `true`.

```javascript
function isPositive( value ) {
    if ( value < 0 ) {
        throw new Error( 'should never reach this line' );
    }
    return ( value > 0 );
}

var obj = {
    'a': 1,
    'b': 2,
    'c': -3,
    'd': 4
};

var bool = someOwnBy( obj, 2, isPositive );
// returns true
```

The invoked `function` is provided three arguments:

-   **value**: object property value.
-   **key**: object property key.
-   **obj**: input object.

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

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

var obj = {
    'a': 1,
    'b': 2,
    'c': 3,
    'd': -5
};

var context = {
    'sum': 0,
    'count': 0
};

var bool = someOwnBy( obj, 1, sum, context );
// returns true

var mean = context.sum / context.count;
// returns 0.25
```

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## Notes

-   An [`Object`][mdn-object] refers to a JavaScript object, which is a collection of properties. Each property is an association between a key (or name) and a value. The key can be a string or a symbol, and the value can be any JavaScript value, including functions and other objects

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

    ```javascript
    function alwaysTrue() {
        return true;
    }
    var bool = someOwnBy( {}, 1, alwaysTrue );
    // returns false
    ```

-   The function does **not** skip `undefined` elements.

    <!-- eslint-disable no-sparse-arrays, stdlib/doctest-marker -->

    ```javascript
    function log( value, key ) {
        console.log( '%s: %s', key, value );
        return ( value < 0 );
    }

    var obj = {
        'a': 1,
        'b': void 0,
        'c': void 0,
        'd': 4,
        'e': -1
    };

    var bool = someOwnBy( obj, 1, log );
    /* =>
        a: 1
        b: void 0
        c: void 0
        d: 4
        e: -1
    */
    ```

-   The function provides limited support for dynamic objects (i.e., objects whose `length` changes during execution).

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## Examples

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

```javascript
var randu = require( '@stdlib/random/base/randu' );
var someOwnBy = require( '@stdlib/utils/some-own-by' );

function threshold( value ) {
    return ( value > 0.95 );
}

var bool;
var obj = {};
var i;

for ( i = 0; i < 100; i++ ) {
    obj[ 'key'+i ] = randu();
}

bool = someOwnBy( obj, 5, threshold );
// returns <boolean>
```

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* * *

## See Also

</section>

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

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