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About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

filter

NPM version Build Status Coverage Status

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

Usage

import filter from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-filter@esm/index.mjs';

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

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@esm/index.mjs';
var isPositiveInteger = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-positive-integer' ).isPrimitive;
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@esm/index.mjs';
import filter from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-filter@esm/index.mjs';

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

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

</script>
</body>
</html>

Notice

This package is part of stdlib, a standard library 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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.