someBy

Test whether a collection contains at least n elements which pass a test implemented by a predicate function.

Usage

var someBy = require( '@stdlib/utils/some-by' );

someBy( collection, n, predicate[, thisArg ] )

Tests whether a collection contains at least n elements which pass a test implemented by a predicate function.

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

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

var bool = someBy( arr, 2, isNegative );
// returns true

Once the function finds n successful elements, the function immediately returns true.

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

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

var bool = someBy( arr, 2, isPositive );
// returns true

The invoked function is provided three arguments:

value: collection element
index: collection index
collection: input collection

To set the function execution context, provide a thisArg.

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

var arr = [ 1, 2, 3, 4, -5 ];

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

var bool = someBy( arr, 1, sum, context );
// returns true

var mean = context.sum / context.count;
// returns 1.0

Notes

A collection may be either an Array, Typed Array, or an array-like Object (excluding strings and functions).

If provided an empty collection, the function returns false.

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

The function does not skip undefined elements.

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

var arr = [ 1, , , 4, -1 ];

var bool = someBy( arr, 1, log );
/* =>
    0: 1
    1: undefined
    2: undefined
    3: 4
    4: -1
*/

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

Examples

var randu = require( '@stdlib/random/base/randu' );
var someBy = require( '@stdlib/utils/some-by' );

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

var bool;
var arr;
var i;

arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
    arr[ i ] = randu();
}

bool = someBy( arr, 5, threshold );
// returns <boolean>

someBy

Usage

someBy( collection, n, predicate[, thisArg ] )

Notes

Examples

See Also