Extremely fast and lightweight double-ended queue implementation with zero dependencies.
Double-ended queues can also be used as a:
This implementation is currently the fastest available, even faster than double-ended-queue
, see the benchmarks
Every queue operation is done at a constant O(1)
- including random access from .peekAt(index)
.
Works on all node versions >= v0.10
npm install denque
const Denque = require("denque");
const denque = new Denque([1,2,3,4]);
denque.shift(); // 1
denque.pop(); // 4
new Denque()
new Denque(Array items)
push(item)
unshift(item)
pop()
shift()
toArray()
peekBack()
peekFront()
peekAt(int index)
isEmpty()
clear()
#####new Denque()
-> Denque
Creates an empty double-ended queue with initial capacity of 4.
var denque = new Denque();
denque.push(1, 2, 3);
denque.shift(); //1
denque.pop(); //3
#####new Denque(Array items)
-> Denque
Creates a double-ended queue from items
.
var denque = new Denque([1,2,3,4]);
denque.shift(); // 1
denque.pop(); // 4
#####push(item)
-> int
Push an item to the back of this queue. Returns the amount of items currently in the queue after the operation.
var denque = new Denque();
denque.push(1);
denque.pop(); // 1
denque.push(2);
denque.push(3);
denque.shift(); // 2
denque.shift(); // 3
#####unshift(item)
-> int
Unshift an item to the front of this queue. Returns the amount of items currently in the queue after the operation.
var denque = new Denque([2,3]);
denque.unshift(1);
denque.toString(); // "1,2,3"
denque.unshift(-2);
denque.toString(); // "-2,-1,0,1,2,3"
#####pop()
-> dynamic
Pop off the item at the back of this queue.
Note: The item will be removed from the queue. If you simply want to see what's at the back of the queue use peekBack()
or .peekAt(-1)
.
If the queue is empty, undefined
is returned. If you need to differentiate between undefined
values in the queue and pop()
return value -
check the queue .length
before popping.
var denque = new Denque([1,2,3]);
denque.pop(); // 3
denque.pop(); // 2
denque.pop(); // 1
denque.pop(); // undefined
Aliases: removeBack
#####shift()
-> dynamic
Shifts off the item at the front of this queue.
Note: The item will be removed from the queue. If you simply want to see what's at the front of the queue use peekFront()
or .peekAt(0)
.
If the queue is empty, undefined
is returned. If you need to differentiate between undefined
values in the queue and shift()
return value -
check the queue .length
before shifting.
var denque = new Denque([1,2,3]);
denque.shift(); // 1
denque.shift(); // 2
denque.shift(); // 3
denque.shift(); // undefined
#####toArray()
-> Array
Returns the items in the queue as an array. Starting from the item in the front of the queue and ending to the item at the back of the queue.
var denque = new Denque([1,2,3]);
denque.push(4);
denque.unshift(0);
denque.toArray(); // [0,1,2,3,4]
#####peekBack()
-> dynamic
Returns the item that is at the back of this queue without removing it.
If the queue is empty, undefined
is returned.
var denque = new Denque([1,2,3]);
denque.push(4);
denque.peekBack(); // 4
#####peekFront()
-> dynamic
Returns the item that is at the front of this queue without removing it.
If the queue is empty, undefined
is returned.
var denque = new Denque([1,2,3]);
denque.push(4);
denque.peekFront(); // 1
#####peekAt(int index)
-> dynamic
Returns the item that is at the given index
of this queue without removing it.
The index is zero-based, so .peekAt(0)
will return the item that is at the front, .peekAt(1)
will return
the item that comes after and so on.
The index can be negative to read items at the back of the queue. .peekAt(-1)
returns the item that is at the back of the queue,
.peekAt(-2)
will return the item that comes before and so on.
Returns undefined
if index
is not a valid index into the queue.
var denque = new Denque([1,2,3]);
denque.peekAt(0); //1
denque.peekAt(1); //2
denque.peekAt(2); //3
denque.peekAt(-1); // 3
denque.peekAt(-2); // 2
denque.peekAt(-3); // 1
Note: The implementation has O(1) random access using .peekAt()
.
Aliases: get
#####isEmpty()
-> boolean
Return true
if this queue is empty, false
otherwise.
var denque = new Denque();
denque.isEmpty(); // true
denque.push(1);
denque.isEmpty(); // false
#####clear()
-> void
Remove all items from this queue. Does not change the queue's capacity.
var denque = new Denque([1,2,3]);
denque.toString(); // "1,2,3"
denque.clear();
denque.toString(); // ""
denque x 31,015,027 ops/sec ±1.52% (86 runs sampled)
double-ended-queue x 21,350,509 ops/sec ±1.21% (86 runs sampled)
denque x 28,710,051 ops/sec ±0.95% (87 runs sampled)
double-ended-queue x 20,531,490 ops/sec ±1.04% (89 runs sampled)