@stdlib/utils-some-own-by NPM

someOwnBy

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

Installation

npm install @stdlib/utils-some-own-by

Usage

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.

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.

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.

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

Notes

An 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.

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

The function does not skip undefined elements.

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).

Examples

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>

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.