npm package: @stdlib/iter-pop
Description: Create an iterator which skips the last value of a provided iterator.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>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.</p>
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</details>

# iterPop

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Create an [iterator][mdn-iterator-protocol] which skips the last value of a provided [iterator][mdn-iterator-protocol].

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/iter-pop
```

</section>

<section class="usage">

## Usage

```javascript
var iterPop = require( '@stdlib/iter-pop' );
```

#### iterPop( iterator\[, clbk\[, thisArg]] )

Returns an [iterator][mdn-iterator-protocol] which skips the last value of a provided [`iterator`][mdn-iterator-protocol].

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

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

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

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

v = it.next().value;
// returns 3

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

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

-   **next**: function which returns an [iterator][mdn-iterator-protocol] 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][mdn-iterator-protocol] is finished.
-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.

To invoke a callback upon skipping the last value of a provided [`iterator`][mdn-iterator-protocol], provide a `clbk` argument.

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

function onPop( v ) {
    console.log( v );
    // => 4
}

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

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

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

v = it.next().value;
// returns 3

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

The callback function is provided a single argument:

-   **v**: the skipped value.

To set the callback execution context, provide a `thisArg`.

<!-- eslint-disable no-invalid-this -->

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

function onPop() {
    this.count += 1;
}

var ctx = {
    'count': 0
};

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

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

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

v = it.next().value;
// returns 3

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

bool = ( ctx.count === 1 );
// returns true
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   If an environment supports `Symbol.iterator` **and** a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random-iter-randu' );
var iterPop = require( '@stdlib/iter-pop' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which skips the last number:
var it = iterPop( rand );

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

</section>

<!-- /.examples -->

<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="references">

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/iter-push`][@stdlib/iter/push]</span><span class="delimiter">: </span><span class="description">create an iterator which appends additional values to the end of a provided iterator.</span>
-   <span class="package-name">[`@stdlib/iter-shift`][@stdlib/iter/shift]</span><span class="delimiter">: </span><span class="description">create an iterator which skips the first value of a provided iterator.</span>
-   <span class="package-name">[`@stdlib/iter-slice`][@stdlib/iter/slice]</span><span class="delimiter">: </span><span class="description">create an iterator which returns a subsequence of iterated values from a provided iterator.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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[npm-image]: http://img.shields.io/npm/v/@stdlib/iter-pop.svg
[npm-url]: https://npmjs.org/package/@stdlib/iter-pop

[test-image]: https://github.com/stdlib-js/iter-pop/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/iter-pop/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-pop/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/iter-pop?branch=main

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[stdlib]: https://github.com/stdlib-js/stdlib

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/iter-pop/tree/deno
[deno-readme]: https://github.com/stdlib-js/iter-pop/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/iter-pop/tree/umd
[umd-readme]: https://github.com/stdlib-js/iter-pop/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/iter-pop/tree/esm
[esm-readme]: https://github.com/stdlib-js/iter-pop/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/iter-pop/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/iter-pop/main/LICENSE

[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

<!-- <related-links> -->

[@stdlib/iter/push]: https://www.npmjs.com/package/@stdlib/iter-push

[@stdlib/iter/shift]: https://www.npmjs.com/package/@stdlib/iter-shift

[@stdlib/iter/slice]: https://www.npmjs.com/package/@stdlib/iter-slice

<!-- </related-links> -->

</section>

<!-- /.links -->