example.js

const exampleSignals =
  'acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab';

const charCount = {};
for (const char of exampleSignals
  .split('')
  .filter((char) => /[a-g]/.test(char))) {
  charCount[char] = (charCount[char] ?? 0) + 1;
}

function charCountSum(signal) {
  return signal.split('').reduce((acc, char) => acc + charCount[char], 0);
}

const charCountSumToDigit = {
  [charCountSum('acedgfb')]: 8,
  [charCountSum('cdfbe')]: 5,
  [charCountSum('gcdfa')]: 2,
  [charCountSum('fbcad')]: 3,
  [charCountSum('dab')]: 7,
  [charCountSum('cefabd')]: 9,
  [charCountSum('cdfgeb')]: 6,
  [charCountSum('eafb')]: 4,
  [charCountSum('cagedb')]: 0,
  [charCountSum('ab')]: 1,
};