filter

Return a shallow copy of an array containing only those elements which pass a test implemented by a predicate function.

Installation

npm install @stdlib/array-base-filter

Usage

var filter = require( '@stdlib/array-base-filter' );

filter( x, predicate[, thisArg] )

Returns a shallow copy of an array containing only those elements which pass a test implemented by a predicate function.

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

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

var out = filter( x, isPositive );
// returns [ 1, 4 ]

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.

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

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

var context = {
    'count': 0
};

var out = filter( x, predicate, context );
// returns [ 1, 2, 4 ]

var cnt = context.count;
// returns 4

Notes

• If provided an array-like object having a filter method, the function defers execution to that method and assumes that the method API has the following signature:

  x.filter( predicate, thisArg )

• If provided an array-like object without a filter method, the function performs a linear scan and always returns a generic array.

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var isPositiveInteger = require( '@stdlib/assert-is-positive-integer' ).isPrimitive;
var naryFunction = require( '@stdlib/utils-nary-function' );
var filter = require( '@stdlib/array-base-filter' );

var x = discreteUniform( 10, -5, 5, {
    'dtype': 'int32'
});
// returns <Int32Array>

var out = filter( x, naryFunction( isPositiveInteger, 1 ) );
// returns <Int32Array>

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.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.