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Michael Lip
Michael Lip

Posted on • Originally published at zovo.one

Morse Code Is a Variable-Length Binary Encoding From 1837

#javascript #webdev #tutorial #beginners

Samuel Morse solved the same problem that Huffman solved with his coding algorithm in 1952: assign shorter codes to more frequent characters. The letter E (the most common in English) is a single dot. The letter J is dot-dash-dash-dash.

The encoding table 

const MORSE = {
  'A': '.-',    'B': '-...',  'C': '-.-.',  'D': '-..',
  'E': '.',     'F': '..-.',  'G': '--.',   'H': '....',
  'I': '..',    'J': '.---',  'K': '-.-',   'L': '.-..',
  'M': '--',    'N': '-.',    'O': '---',   'P': '.--.',
  'Q': '--.-',  'R': '.-.',   'S': '...',   'T': '-',
  'U': '..-',   'V': '...-',  'W': '.--',   'X': '-..-',
  'Y': '-.--',  'Z': '--..',
  '0': '-----', '1': '.----', '2': '..---', '3': '...--',
  '4': '....-', '5': '.....', '6': '-....', '7': '--...',
  '8': '---..', '9': '----.'
};
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The variable-length insight

Morse assigned the shortest codes to the most frequent English letters. E (12.7% frequency) is a single dot. T (9.1%) is a single dash. Compare that to Q (0.1%) which is dash-dash-dot-dash.

This is the same principle behind Huffman coding, invented over a century later. Frequently occurring symbols get shorter codes, minimizing total message length. Morse figured this out empirically by counting letter frequencies in a printer's type case.

Encoding and decoding 

function textToMorse(text) {
  return text.toUpperCase().split('').map(char => {
    if (char === ' ') return '/';
    return MORSE[char] || '';
  }).join(' ');
}

function morseToText(morse) {
  const REVERSE = Object.fromEntries(
    Object.entries(MORSE).map(([k, v]) => [v, k])
  );

  return morse.split(' / ').map(word =>
    word.split(' ').map(code => REVERSE[code] || '').join('')
  ).join(' ');
}
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The convention is: spaces between letters, slashes (or triple spaces) between words.

Timing in audio Morse

When generating audible Morse code, the timing ratios matter:

  • Dot duration: 1 unit
  • Dash duration: 3 units
  • Space between elements of same letter: 1 unit
  • Space between letters: 3 units
  • Space between words: 7 units

At 20 words per minute (standard proficiency), one unit is 60 milliseconds.

For translating text to and from Morse code with audio playback, I built a translator at zovo.one/free-tools/morse-code-translator. It handles both directions and plays the encoded message as audio with proper timing ratios.

I'm Michael Lip. I build free developer tools at zovo.one. 500+ tools, all private, all free.

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