Beginner Exercism • javascript

Wordy

Challenge Overview

Parse and evaluate simple math word problems returning the answer as an integer.

💡 View Solution

export const answer = (question) => {
  const match = question.match(/^What is (.*)\?$/);
  if (!match) throw new Error('Unknown operation');

  const tokens = match[1]
    .replace(/plus/g, '+')
    .replace(/minus/g, '-')
    .replace(/multiplied by/g, '*')
    .replace(/divided by/g, '/')
    .split(' ');

  if (tokens.length === 0 || tokens[0] === '') throw new Error('Unknown operation');

  let res = parseInt(tokens[0]);
  if (isNaN(res)) throw new Error('Unknown operation');

  for (let i = 1; i < tokens.length; i += 2) {
    const op = tokens[i];
    const val = parseInt(tokens[i + 1]);

    if (isNaN(val)) {
       if (tokens[i] && !['+', '-', '*', '/'].includes(tokens[i])) {
         throw new Error('Unknown operation');
       }
       throw new Error('Syntax error');
    }

    switch (op) {
      case '+': res += val; break;
      case '-': res -= val; break;
      case '*': res *= val; break;
      case '/': res /= val; break;
      default: throw new Error('Unknown operation');
    }
  }

  return res;
};