Stack

Stack data structure.

Installation

npm install @stdlib/utils-stack

Usage

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

stack()

Returns a Stack instance.

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

s.clear()

Clears a stack.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Notes

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

Examples

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

See Also

• @stdlib/utils-fifo: first-in-first-out (FIFO) queue.

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.