npm package: @stdlib/utils-stack
Description: Stack.
Author: The Stdlib Authors
Latest version: 0.2.2

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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>

# Stack

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

> Stack data structure.

<!-- 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/utils-stack
```

</section>

<section class="usage">

## Usage

```javascript
var stack = require( '@stdlib/utils-stack' );
```

#### stack()

Returns a `Stack` instance.

```javascript
var s = stack();
// returns <Stack>
```

##### s.clear()

Clears a stack.

```javascript
var s = stack();
// returns <Stack>

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Peek at the top value:
var v = s.first();
// returns 'bar'

// Examine the stack length:
var len = s.length;
// returns 2

// Clear all stack items:
s.clear();

// Peek at the top value:
v = s.first();
// returns undefined

// Examine the stack length:
len = s.length;
// returns 0
```

##### s.first()

Returns the top stack value (i.e., the value which is "first-out"). If the stack is currently empty, the returned value is `undefined`.

```javascript
var s = stack();
// returns <Stack>

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Peek at the top value:
var v = s.first();
// returns 'bar'
```

##### s.iterator()

Returns an iterator for iterating over a stack. If an environment supports `Symbol.iterator`, the returned iterator is iterable.

```javascript
var s = stack();

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Create an iterator:
var it = s.iterator();

// Iterate over the stack...
var v = it.next().value;
// returns 'bar'

v = it.next().value;
// returns 'foo'

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

**Note**: in order to prevent confusion arising from stack mutation during iteration, a returned iterator **always** iterates over a stack "snapshot", which is defined as the list of stack elements at the time of `s.iterator()` invocation.

##### s.last()

Returns the bottom stack value (i.e., the value which is "last-out"). If the stack is currently empty, the returned value is `undefined`.

```javascript
var s = stack();
// returns <Stack>

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Peek at the bottom value:
var v = s.last();
// returns 'foo'
```

##### s.length

Stack length.

```javascript
var s = stack();

// Examine the initial stack length:
var len = s.length;
// returns 0

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Retrieve the current stack length:
len = s.length;
// returns 2
```

##### s.pop()

Removes a value from the stack. If the stack is currently empty, the returned value is `undefined`.

```javascript
var s = stack();

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Remove the top value:
var v = s.pop();
// returns 'bar'

// Add a new value to the stack:
s.push( 'beep' );

// Remove the top value:
v = s.pop();
// returns 'beep'
```

##### s.push( value )

Adds a value to the stack.

```javascript
var s = stack();

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Remove the top value:
var v = s.pop();
// returns 'bar'

// Add a new value to the stack:
s.push( 'beep' );

// Remove the top value:
v = s.pop();
// returns 'beep'
```

##### s.toArray()

Returns an array of stack values.

```javascript
var s = stack();

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Get an array of stack values:
var vals = s.toArray();
// returns [ 'bar', 'foo' ]
```

**Note**: the order of the returned array is reverse stack insertion order (i.e., the "newest" stack elements come before the "oldest" stack elements).

##### s.toJSON()

Serializes a stack as JSON.

```javascript
var s = stack();

// Add values to the stack:
s.push( 'foo' ).push( 'bar' );

// Serialize to JSON:
var o = s.toJSON();
// returns { 'type': 'stack', 'data': [ 'bar', 'foo' ] }
```

**Note**: `JSON.stringify()` implicitly calls this method when stringifying a stack instance.

</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

-   A stack is also known as a Last-In-First-Out (LIFO) queue.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

<!-- eslint-disable stdlib/no-redeclare -->

```javascript
var Stack = require( '@stdlib/utils-stack' );

var stack;
var iter;
var len;
var v;
var i;

// Create a new stack:
stack = new Stack();

// Add some values to the stack:
stack.push( 'foo' );
stack.push( 'bar' );
stack.push( 'beep' );
stack.push( 'boop' );

// Peek at the top and bottom stack values:
v = stack.first();
// returns 'boop'

v = stack.last();
// returns 'foo'

// Inspect the stack length:
len = stack.length;
// returns 4

// Remove the top value:
v = stack.pop();
// returns 'boop'

// Inspect the stack length:
len = stack.length;
// returns 3

// Iterate over the stack:
iter = stack.iterator();
for ( i = 0; i < len; i++ ) {
    console.log( 'Stack value #%d: %s', i+1, iter.next().value );
}

// Clear the stack:
stack.clear();

// Inspect the stack length:
len = stack.length;
// returns 0
```

</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 -->

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/utils-fifo`][@stdlib/utils/fifo]</span><span class="delimiter">: </span><span class="description">first-in-first-out (FIFO) queue.</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; 2016-2024. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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<section class="links">

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

[test-image]: https://github.com/stdlib-js/utils-stack/actions/workflows/test.yml/badge.svg?branch=v0.2.2
[test-url]: https://github.com/stdlib-js/utils-stack/actions/workflows/test.yml?query=branch:v0.2.2

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-stack/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-stack?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/utils-stack/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-stack/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-stack/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-stack/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-stack/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-stack/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-stack/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-stack/main/LICENSE

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[@stdlib/utils/fifo]: https://www.npmjs.com/package/@stdlib/utils-fifo

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</section>

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