49 lines
912 B
JavaScript
49 lines
912 B
JavaScript
function Queue () {
|
|
this.head = new Item('head', null)
|
|
}
|
|
module.exports = Queue
|
|
|
|
Queue.prototype.append = function append (kind, value) {
|
|
var item = new Item(kind, value)
|
|
this.head.prepend(item)
|
|
return item
|
|
}
|
|
|
|
Queue.prototype.isEmpty = function isEmpty () {
|
|
return this.head.prev === this.head
|
|
}
|
|
|
|
Queue.prototype.first = function first () {
|
|
return this.head.next
|
|
}
|
|
|
|
function Item (kind, value) {
|
|
this.prev = this
|
|
this.next = this
|
|
this.kind = kind
|
|
this.value = value
|
|
}
|
|
|
|
Item.prototype.prepend = function prepend (other) {
|
|
other.prev = this.prev
|
|
other.next = this
|
|
other.prev.next = other
|
|
other.next.prev = other
|
|
}
|
|
|
|
Item.prototype.dequeue = function dequeue () {
|
|
var prev = this.prev
|
|
var next = this.next
|
|
|
|
prev.next = next
|
|
next.prev = prev
|
|
this.prev = this
|
|
this.next = this
|
|
|
|
return this.value
|
|
}
|
|
|
|
Item.prototype.isEmpty = function isEmpty () {
|
|
return this.prev === this
|
|
}
|