Find

Find elements in an array-like object that satisfy a test condition.

Installation

npm install @stdlib/utils-find

Usage

var find = require( '@stdlib/utils-find' );

find( arr, [opts,] clbk )

Finds elements in an array-like object that satisfy a test condition. The function accepts two options: k and returns.

• k: an integer which limits the number of elements returned and whose sign determines the direction in which to search. If set to a negative integer, the function searches from the last element to the first element.

• returns: specifies the type of result to return and may be one of three options: indices, values, *.

  • indices: indicates to return the element indices of those elements satisfying the search condition.
  • values: indicates to return the element values of those elements satisfying the search condition.
  • *: indicates to return both the element indices and values of those elements satisfying the search condition. The returned result is an array of arrays, where each sub-array is an index-value pair.

The callback is provided three arguments:

• element: the current element
• index: the current element's index
• array: the input array, typed array or string

By default, k is the length of arr and returns is set to indices.

var data = [ 30, 20, 50, 60, 10 ];

function greaterThan20( val ) {
    return val > 20;
}

var vals = find( data, greaterThan20 );
// returns [ 0, 2, 3 ]

data = 'Hello World';
function isUpperCase( val ) {
    return /[A-Z]/.test( val );
}

vals = find( data, isUpperCase );
// returns [ 0, 6 ]

To limit the number of results and specify that values should be returned,

var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': 2,
    'returns': 'values'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 30, 50 ]

If no array elements satisfy the test condition, the function returns an empty array.

var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': 2,
    'returns': 'values'
};

function condition( val ) {
    return val > 1000;
}

var vals = find( data, opts, condition );
// returns []

To find the last two values satisfying a search condition,

var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': 'values'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 60, 50 ]

To explicitly specify that only indices are returned,

var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': 'indices'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ 3, 2 ]

And to return both indices and values as index-value pairs,

var data = [ 30, 20, 50, 60, 10 ];

var opts = {
    'k': -2,
    'returns': '*'
};

function condition( val ) {
    return val > 20;
}

var vals = find( data, opts, condition );
// returns [ [3, 60], [2, 50] ]

Examples

var round = require( '@stdlib/math-base-special-round' );
var randu = require( '@stdlib/random-base-randu' );
var find = require( '@stdlib/utils-find' );

// Simulate the data...
var data = new Array( 100 );
var i;
for ( i = 0; i < data.length; i++ ) {
    data[ i ] = round( randu*100 );
}

// Find the first 10 values greater than 25...
var opts = {
    'k': 10,
    'returns': '*'
};

function condition( val ) {
    return val > 25;
}

var vals = find( data, opts, condition );
console.log( vals.join( '\n' ) );

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.