n-ary-huffman

Overview

var huffman = require("n-ary-huffman")
 
var names = ["Alfa", "Bravo", "Charlie", "Delta", "Echo", "Foxtrot", "Golf"]
var items = names.map(function(name, index) {
  return {
    name: name,
    weight: index,
    codeWord: null
  }
})
 
var alphabet = "0123"
 
var tree = huffman.createTree(items, alphabet.length)
tree.assignCodeWords(alphabet, function(item, codeWord) {
  item.codeWord = codeWord
})
 
console.log(items)
// [
//   { name: 'Alfa',    weight: 0, codeWord: '13' },
//   { name: 'Bravo',   weight: 1, codeWord: '12' },
//   { name: 'Charlie', weight: 2, codeWord: '11' },
//   { name: 'Delta',   weight: 3, codeWord: '10' },
//   { name: 'Echo',    weight: 4, codeWord: '3'  },
//   { name: 'Foxtrot', weight: 5, codeWord: '2'  },
//   { name: 'Golf',    weight: 6, codeWord: '0'  }
// ]

Installation

npm install n-ary-huffman

var huffman = require('n-ary-huffman')

Usage

createTree(elements, n, [options])

elements is an array of objects. Each object is expected to have a weight property which represents the weight of the object, which is a number.

Returns a new BranchPoint—the root of an n-ary huffman tree, consisting of all the items in elements as well as BranchPoints. Each BranchPoint has n children (except the deepest one which might have fewer, depending on elements.length).

options:

• sorted: Boolean. Defaults to false. In order to create the tree, elements needs to be sorted after the weights in descending order. Enable this option if elements already is sorted this way, to skip sorting again.

new BranchPoint(children, weight)

Instance properties:

• children: children
• weight: weight

See createTree(…) above for more information.

BranchPoint.prototype.assignCodeWords(alphabet, callback, prefix="")

Assign a code word to each element in the tree. The larger the weight of an element, the shorter the code word.

alphabet is a string or an array of characters to use for the code words. Make sure that the alphabet is at least as long the arity of the tree. Note: Don’t repeat characters, or you’ll get invalid code words.

callback(element, codeWord) is run for each object in the tree.

prefix (optional) will be added at the beginning of each code word.

License

The X11 “MIT” License.