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Count the number of elements in an array which pass a test implemented by a predicate function.
To use in Observable,
countIf = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/array-base-count-if@umd/browser.js' )
To vendor stdlib functionality and avoid installing dependency trees for Node.js, you can use the UMD server build:
var countIf = require( 'path/to/vendor/umd/array-base-count-if/index.js' )
To include the bundle in a webpage,
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/array-base-count-if@umd/browser.js"></script>
If no recognized module system is present, access bundle contents via the global scope:
<script type="text/javascript">
(function () {
window.countIf;
})();
</script>
Counts the number of elements in an array which pass a test implemented by a predicate function.
function predicate( value ) {
return ( value > 0 );
}
var x = [ 0, 1, 0, 1, 2 ];
var out = countIf( x, predicate );
// returns 3
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 = [ 0, 1, 0, 1, 2 ];
var context = {
'count': 0
};
var out = countIf( x, predicate, context );
// returns 3
var cnt = context.count;
// returns 5
<!DOCTYPE html>
<html lang="en">
<body>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-positive-integer@umd/browser.js"></script>
<script type="text/javascript">
(function () {.isPrimitive;
var naryFunction = require( '@stdlib/utils-nary-function' );
var countIf = require( '@stdlib/array-base-count-if' );
var x = discreteUniform( 10, -5, 5, {
'dtype': 'int32'
});
// returns <Int32Array>
var out = countIf( x, naryFunction( isPositiveInteger, 1 ) );
// returns <number>
console.log( x );
console.log( out );
})();
</script>
</body>
</html>
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.
See LICENSE.
Copyright © 2016-2024. The Stdlib Authors.