spamfilter.js

const alphabetMap = {
  a: 'a@4', b: 'b8', c: 'c{\\[(', d: 'd', e: 'e3', f: 'f', g: 'g69', h: 'h',
  i: 'i|', j: 'j', k: 'k', l: 'l', m: 'm', n: 'n', o: 'o0', p: 'p', q: 'q',
  r: 'r', s: 's5', t: 't7', u: 'u', v: 'v', w: 'w', x: 'x', y: 'y', z: 'z2'
};

const makeRegex = str => {
  const inner = str.split('').map(char => {
    const chars = alphabetMap[char];

    return (!chars || chars.length === 1)
      ? char
      : `[${chars}]`;
  });

  return new RegExp(`\\b${inner.join('\\s*')}\\b`, 'i');
};

const spamPhrases = [
  'viagra', 'free money', 'work from home', 'stock alert', 'dear friend'
];

const regexps = spamPhrases.map(phrase => makeRegex(phrase));

const isSpam = msg => {
  return regexps.some(re => re.test(msg));
};

const tests = [
  [ 'fr33 m0ney' , true ],
  [ 'F R E E   M O N E Y', true ],
  [ 'w0rk   from   h0m3' , true ],
  [ 'great d3als 0n VI4GR4!', true ],
  [ 'Hello John,', false ],
  [ 'The PPT from the meeting is attached', false ],
  [ '', false ]
];

tests.forEach(test => {
  console.assert(isSpam(test[0]) === test[1]);
});