FIFO

First-in-first-out (FIFO) queue.

Installation

npm install @stdlib/utils-fifo

Usage

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

fifo()

Returns a new first-in-first-out (FIFO) queue instance.

var queue = fifo();
// returns <FIFO>

queue.clear()

Clears a queue.

var queue = fifo();
// returns <FIFO>

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

// Peek at the first value:
var v = queue.first();
// returns 'foo'

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

// Clear all queue items:
queue.clear();

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

// Examine the queue length:
len = queue.length;
// returns 0

queue.first()

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

var queue = fifo();
// returns <FIFO>

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

// Peek at the first value:
var v = queue.first();
// returns 'foo'

queue.iterator()

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

var queue = fifo();

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

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

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

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

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

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

queue.last()

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

var queue = fifo();
// returns <FIFO>

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

// Peek at the last value:
var v = queue.last();
// returns 'bar'

queue.length

Queue length.

var queue = fifo();

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

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

// Retrieve the current queue length:
len = queue.length;
// returns 2

queue.pop()

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

var queue = fifo();

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

// Remove the first value:
var v = queue.pop();
// returns 'foo'

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

// Remove the "oldest" queue value:
v = queue.pop();
// returns 'bar'

queue.push( value )

Adds a value to the queue.

var queue = fifo();

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

// Remove the first value:
var v = queue.pop();
// returns 'foo'

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

// Remove the "oldest" queue value:
v = queue.pop();
// returns 'bar'

queue.toArray()

Returns an array of queue values.

var queue = fifo();

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

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

queue.toJSON()

Serializes a queue as JSON.

var queue = fifo();

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

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

Note: JSON.stringify() implicitly calls this method when stringifying a queue instance.

Examples

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

var queue;
var iter;
var len;
var v;
var i;

// Create a new FIFO queue:
queue = fifo();

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

// Peek at the first and last queue values:
v = queue.first();
// returns 'foo'

v = queue.last();
// returns 'boop'

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

// Remove the "oldest" queue value:
v = queue.pop();
// returns 'foo'

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

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

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

// Inspect the queue length:
len = queue.length;
// returns 0

See Also

• @stdlib/utils-stack: stack.

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.