Huffman Compression Algorithm Comments

Compression/Huffman.js

@@ -1,4 +1,3 @@
-
 /**
  * Huffman Coding is a lossless data compression algorithm that uses variable-length codes to represent characters.
  *
@@ -18,16 +17,15 @@
  * @returns {Object} - The frequency table.
  */
 function buildFrequencyTable(data) {
-  const freqTable = {}
+ const freqTable = {}
 
-  for (const char of data) {
-  freqTable[char] = (freqTable[char] || 0) + 1
-  }
+ for (const char of data) {
+ freqTable[char] = (freqTable[char] || 0) + 1
+ }
 
-  return freqTable
+ return freqTable
 }
 
-
 /**
  * A Huffman Node is a node in a Huffman tree.
  * @class HuffmanNode
@@ -37,35 +35,35 @@ function buildFrequencyTable(data) {
  * @property {HuffmanNode} right - The right child of the node.
  */
 class HuffmanNode {
-  constructor(char, freq) {
-  this.char = char
-  this.freq = freq
-  this.left = null
-  this.right = null
-  }
+ constructor(char, freq) {
+ this.char = char
+ this.freq = freq
+ this.left = null
+ this.right = null
+ }
 }
 
 /**
- * Builds a Huffman tree from a frequency table. 
+ * Builds a Huffman tree from a frequency table.
  * @param {Object} freqTable - The frequency table to use for building the tree.
  * @returns {HuffmanNode} - The root node of the Huffman tree.
  */
 function buildHuffmanTree(freqTable) {
-  const nodes = Object.keys(freqTable).map(
-  (char) => new HuffmanNode(char, freqTable[char])
-  )
-
-  while (nodes.length > 1) {
-  nodes.sort((a, b) => a.freq - b.freq)
-  const left = nodes.shift()
-  const right = nodes.shift()
-  const parent = new HuffmanNode(null, left.freq + right.freq)
-  parent.left = left
-  parent.right = right
-  nodes.push(parent)
-  }
-
-  return nodes[0]
+ const nodes = Object.keys(freqTable).map(
+ (char) => new HuffmanNode(char, freqTable[char])
+ )
+
+ while (nodes.length > 1) {
+ nodes.sort((a, b) => a.freq - b.freq)
+ const left = nodes.shift()
+ const right = nodes.shift()
+ const parent = new HuffmanNode(null, left.freq + right.freq)
+ parent.left = left
+ parent.right = right
+ nodes.push(parent)
+ }
+
+ return nodes[0]
 }
 
 /**
@@ -76,14 +74,14 @@ function buildHuffmanTree(freqTable) {
  * @returns {Object} - The Huffman code table.
  */
 function buildHuffmanCodes(root, prefix = '', codes = {}) {
- if (root) {
- if (root.char) {
- codes[root.char] = prefix
- }
- buildHuffmanCodes(root.left, prefix + '0', codes)
- buildHuffmanCodes(root.right, prefix + '1', codes)
+ if (root) {
+ if (root.char) {
+ codes[root.char] = prefix
  }
- return codes
+ buildHuffmanCodes(root.left, prefix + '0', codes)
+ buildHuffmanCodes(root.right, prefix + '1', codes)
+ }
+ return codes
 }
 
 /**
@@ -93,15 +91,15 @@ function buildHuffmanCodes(root, prefix = '', codes = {}) {
  * @returns {string} - The encoded string.
  */
 function encodeHuffman(data, freqTable) {
-  const root = buildHuffmanTree(freqTable)
-  const codes = buildHuffmanCodes(root)
+ const root = buildHuffmanTree(freqTable)
+ const codes = buildHuffmanCodes(root)
 
-  let encodedData = ''
-  for (let char of data) {
-  encodedData += codes[char]
-  }
+ let encodedData = ''
+ for (let char of data) {
+ encodedData += codes[char]
+ }
 
-  return encodedData
+ return encodedData
 }
 
 /**
@@ -111,22 +109,22 @@ function encodeHuffman(data, freqTable) {
  * @returns {string} - The decoded string.
  */
 function decodeHuffman(encodedData, root) {
- let decodedData = ''
- let currentNode = root
- for (let bit of encodedData) {
- if (bit === '0') {
- currentNode = currentNode.left
- } else {
- currentNode = currentNode.right
- }
-
- if (currentNode.char) {
- decodedData += currentNode.char
- currentNode = root
- }
+ let decodedData = ''
+ let currentNode = root
+ for (let bit of encodedData) {
+ if (bit === '0') {
+ currentNode = currentNode.left
+ } else {
+ currentNode = currentNode.right
+ }
+
+ if (currentNode.char) {
+ decodedData += currentNode.char
+ currentNode = root
  }
+ }
 
-  return decodedData
+ return decodedData
 }
 
 // Example usage
@@ -140,9 +138,9 @@ const decodedData = decodeHuffman(encodedData, root)
 console.log('Decoded Data:', decodedData)
 
 export {
-  buildHuffmanCodes,
-  buildHuffmanTree,
-  encodeHuffman,
-  decodeHuffman,
-  buildFrequencyTable
+ buildHuffmanCodes,
+ buildHuffmanTree,
+ encodeHuffman,
+ decodeHuffman,
+ buildFrequencyTable
 }