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A fast O(1) push/pop/shift/unshift thing

branch: master
README.md

The Problem

You've got some thing where you need to push a bunch of stuff into a queue and then shift it out. Or, maybe, you need to pop it out stack-like, but it's not clear at the outset which way it's going to go.

Arrays work for this, but are a bit costly performance-wise in the mixed case. In the pure-stack case (or, as of recent V8 versions, the pure-queue case as well), Arrays are best.

In cases where it's mixed, a linked list implementation can be significantly faster. See the benchmark scripts in bench/*.js to measure the differences.

This lacks a lot of features that arrays have:

  1. You can't specify the size at the outset.
  2. It's not indexable.
  3. There's no join, concat, etc.

If any of this matters for your use case, you're probably better off using an Array object.

If you know that you'll be using it as a stack or a queue exclusively, then you're better off using an Array object.

If you know the eventual size at the offset, then you're definitely better off using an Array.

Installing

npm install fast-list

API

var FastList = require("fast-list")
var list = new FastList()
list.push("foo")
list.unshift("bar")
list.push("baz")
console.log(list.length) // 2
console.log(list.pop()) // baz
console.log(list.shift()) // bar
console.log(list.shift()) // foo

Methods

  • push: Just like Array.push, but only can take a single entry
  • pop: Just like Array.pop. Note: if you're only using push and pop, then you have a stack, and Arrays are better for that.
  • shift: Just like Array.shift. Note: if you're only using push and shift, then you have a queue, and Arrays are better for that.
  • unshift: Just like Array.unshift, but only can take a single entry.
  • drop: Drop all entries
  • item(n): Retrieve the nth item in the list. This involves a walk every time. It's very slow. If you find yourself using this, consider using a normal Array instead.
  • map(fn, thisp): Like Array.prototype.map. Returns a new FastList.
  • reduce(fn, startValue, thisp): Like Array.prototype.reduce
  • forEach(fn, this): Like Array.prototype.forEach
  • filter(fn, thisp): Like Array.prototype.filter. Returns a new FastList.
  • slice(start, end): Retrieve an array of the items at this position. This involves a walk every time. It's very slow. If you find yourself using this, consider using a normal Array instead.

Members

  • length: The number of things in the list. Note that, unlike Array.length, this is not a getter/setter, but rather a counter that is internally managed. Setting it can only cause harm.
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