@stdlib/iter-head NPM

iterHead

Create an iterator which returns the first n values of a provided iterator.

Installation

npm install @stdlib/iter-head

Usage

var iterHead = require( '@stdlib/iter-head' );

iterHead( iterator, n )

Returns an iterator which returns the first n values of a provided iterator.

var array2iterator = require( '@stdlib/array-to-iterator' );

var it = iterHead( array2iterator( [ 1, 2, 3, 4 ] ), 2 );
// returns <Object>

var v = it.next().value;
// returns 1

v = it.next().value;
// returns 2

var bool = it.next().done;
// returns true

The returned iterator protocol-compliant object has the following properties:

next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

Notes

If a provided iterator only generates m values and m is less than n, the returned iterator only returns m values.
If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.

Examples

var randu = require( '@stdlib/random-iter-randu' );
var iterHead = require( '@stdlib/iter-head' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234
});

// Create an iterator which returns the first 10 generated numbers:
var it = iterHead( rand, 10 );

// Perform manual iteration...
var r;
while ( true ) {
    r = it.next();
    if ( r.done ) {
        break;
    }
    console.log( r.value );
}

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.