Morse Code in JavaScript: Encoder & Decoder Guide

Morse code encodes text as sequences of dots (short signals) and dashes (long signals). Each letter and digit maps to a unique dot-dash pattern. Implementing a Morse code encoder and decoder in JavaScript is a practical exercise in hash map lookups, string manipulation, and audio synthesis (if you want to play the beeps). This guide covers a complete, working implementation you can drop into any project.

How to Use the Morse Code Converter Tool

1. Enter text — Type a message in the text field. The tool encodes it to Morse code instantly.
2. Or enter Morse code — Paste dots and dashes (separated by spaces for letters, slashes for words) to decode back to text.
3. Copy the result — Use the copy button to grab the encoded or decoded output.
4. Use the code below — Implement the same encoder/decoder in your own JavaScript application.

Morse Code Encoder in JavaScript

const MORSE_CODE = {
  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': '----.'
};

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

console.log(textToMorse('HELLO WORLD'));
// .... . .-.. .-.. --- / .-- --- .-. .-.. -..

Morse Code Decoder in JavaScript

const REVERSE_MORSE = Object.fromEntries(
  Object.entries(MORSE_CODE).map(([k, v]) => [v, k])
);

function morseToText(morse) {
  return morse
    .split(' / ')
    .map(word =>
      word.split(' ').map(code => REVERSE_MORSE[code] || '?').join('')
    )
    .join(' ');
}

console.log(morseToText('.... . .-.. .-.. --- / .-- --- .-. .-.. -..'));
// HELLO WORLD

Playing Morse Code Audio in the Browser

async function playMorse(morse, wpm = 20) {
  const ctx = new AudioContext();
  const dotDuration = 1200 / wpm / 1000; // seconds
  let time = ctx.currentTime;

  for (const symbol of morse) {
    if (symbol === '.') {
      playTone(ctx, time, dotDuration);
      time += dotDuration * 2;
    } else if (symbol === '-') {
      playTone(ctx, time, dotDuration * 3);
      time += dotDuration * 4;
    } else if (symbol === ' ') {
      time += dotDuration * 3;
    } else if (symbol === '/') {
      time += dotDuration * 7;
    }
  }
}

function playTone(ctx, startTime, duration) {
  const osc = ctx.createOscillator();
  const gain = ctx.createGain();
  osc.connect(gain);
  gain.connect(ctx.destination);
  osc.frequency.value = 600; // Hz
  osc.start(startTime);
  osc.stop(startTime + duration);
}

Why Implement Morse Code in JavaScript?

• Educational projects — Morse code converters are excellent practice for hash map lookups, string splitting, and array mapping.
• Accessibility tools — Morse code can be an input method for users with motor impairments, using single-switch devices.
• Audio feedback UIs — The Web Audio API integration lets you play audible Morse signals directly in the browser.
• Encoding challenges — Morse code is a good starting point for understanding encoding systems, substitution ciphers, and data transformation.

Test your Morse code conversions with the Morse Code Converter — encode and decode text instantly.