@coffeeandfun/maths-captcha/src/question-types/arithmetic.js

Maths-Captcha is a simple Node.js module that generates random math questions to verify human interaction. It creates math problems like addition, subtraction, multiplication, division, powers, percentages, sequences, and algebra, and checks if the user's

import { randomInt, randomChoice, randomIntInRange } from '../random.js';

const OPERATION_FUNCTIONS = {
  '+': (a, b) => a + b,
  '-': (a, b) => a - b,
  '*': (a, b) => a * b,
  '/': (a, b) => a / b,
  '%': (a, b) => a % b,
};

export const SUPPORTED_OPERATIONS = Object.keys(OPERATION_FUNCTIONS);

export function generateArithmetic(config) {
  const allowedOperations = config.OPERATIONS.filter((op) =>
    SUPPORTED_OPERATIONS.includes(op),
  );
  const operations = allowedOperations.length
    ? allowedOperations
    : ['+', '-', '*', '/'];

  for (let attempt = 0; attempt < config.MAX_ATTEMPTS; attempt++) {
    const candidate = buildCandidate(operations, config);
    if (candidate) return candidate;
  }

  return buildSafeAddition(config);
}

function buildCandidate(operations, config) {
  let num1 = randomIntInRange(config.NUMBER_RANGE);
  let num2 = randomIntInRange(config.NUMBER_RANGE);
  const operation = randomChoice(operations);

  if (operation === '-' && config.AVOID_NEGATIVE_RESULTS && num1 < num2) {
    [num1, num2] = [num2, num1];
  }

  if (operation === '/' && config.AVOID_DIVISION_BY_ZERO && num2 === 0) {
    return null;
  }

  if (operation === '%' && num2 === 0) {
    return null;
  }

  const compute = OPERATION_FUNCTIONS[operation];
  const numericResult = compute(num1, num2);

  if (config.AVOID_NEGATIVE_RESULTS && numericResult < 0) {
    return null;
  }

  const formattedAnswer =
    operation === '/'
      ? numericResult.toFixed(config.DIVISION_PRECISION)
      : numericResult.toString();

  return {
    question: `${num1} ${operation} ${num2}`,
    answer: formattedAnswer,
    numericAnswer: numericResult,
    operation,
    operands: [num1, num2],
    type: 'arithmetic',
  };
}

function buildSafeAddition(config) {
  const num1 = randomInt(1, 10);
  const num2 = randomInt(1, 10);
  const result = num1 + num2;
  return {
    question: `${num1} + ${num2}`,
    answer: result.toString(),
    numericAnswer: result,
    operation: '+',
    operands: [num1, num2],
    type: 'arithmetic',
  };
}