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A data structure for groups of identical objects, up to a maximum number. Useful for games. (This module was previously known as "itemstack".)

Build Status

Can be used standalone but most useful with inventory.

Requires a ES6-compatible environment (at least partially), tested on Node v4.2.4


An item pile can be created simply with an item name and count, for example:

var ItemPile = require('itempile');

var x = new ItemPile('dirt', 10);

represents a quantity of 10 dirt. The item type can be an any comparable object (singleton); these examples use strings. The quantity can be omitted to use a default of "1".


Piles of the same type can be merged:

var a = new ItemPile('dirt', 10);
var b = new ItemPile('dirt', 20);


results in a increasing to 30 and b to 0. mergePile returns false if the piles differ in type and cannot be merged, otherwise the number of items that did not fit (excess above the maximum pile size):

var a = new ItemPile('dirt', 1);
var b = new ItemPile('dirt', 80);


increases the count of a to 64, the default ItemPile.maxStackSize limit, and decreases b to 17. The sum of the two pile counts remains invariant, the quantity has just shifted between the two.


Want to take items from a pile? Split the pile, specifying the number of items you want:

var a = new ItemPile('dirt', 64)
var b = a.splitPile(16)

b is a new pile with 16 dirt, a is lowered to the remaining 48 dirt. For convenience you can alternatively pass a decimal fraction (such as 0.5, splits the pile in half), or a negative integer (-1 to take all but one).

Other operations

Merging/splitting are the most important but several other methods are provided, see the unit tests for further examples.

Advanced piles

You can create piles of infinite size:

new ItemPile('diamond', Infinity)

and they behave as you expect, sinking unlimited items when merging and sourcing unlimited items when splitting.

Extra data can be attached to a pile, using the "tags" parameter:

new ItemPile('pick', 1, {damage:0})