@coffeeandfun/maths-captcha/src/question-types/pemdas.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 } from '../random.js';

const SAFE_OPERATIONS = ['+', '-', '*'];
const COMPUTE = {
  '+': (a, b) => a + b,
  '-': (a, b) => a - b,
  '*': (a, b) => a * b,
};

export function generatePemdas(config) {
  const useParentheses = Math.random() < 0.4;
  const num1 = randomInt(2, 12);
  const num2 = randomInt(2, 12);
  const num3 = randomInt(2, 12);
  const op1 = randomChoice(SAFE_OPERATIONS);
  const op2 = randomChoice(SAFE_OPERATIONS);

  const { question, answer } = useParentheses
    ? buildParenthesized(num1, op1, num2, op2, num3)
    : buildPrecedence(num1, op1, num2, op2, num3);

  if (config.AVOID_NEGATIVE_RESULTS && answer < 0) {
    return generatePemdas(config);
  }

  return {
    question,
    answer: answer.toString(),
    numericAnswer: answer,
    operation: 'expr',
    operands: [num1, num2, num3],
    type: 'pemdas',
  };
}

function buildPrecedence(num1, op1, num2, op2, num3) {
  const op1IsHigher = op1 === '*';
  const op2IsHigher = op2 === '*';

  let answer;
  if (op1IsHigher && !op2IsHigher) {
    answer = COMPUTE[op2](COMPUTE[op1](num1, num2), num3);
  } else if (!op1IsHigher && op2IsHigher) {
    answer = COMPUTE[op1](num1, COMPUTE[op2](num2, num3));
  } else {
    answer = COMPUTE[op2](COMPUTE[op1](num1, num2), num3);
  }

  return {
    question: `${num1} ${op1} ${num2} ${op2} ${num3}`,
    answer,
  };
}

function buildParenthesized(num1, op1, num2, op2, num3) {
  const wrapLeft = Math.random() < 0.5;
  if (wrapLeft) {
    return {
      question: `(${num1} ${op1} ${num2}) ${op2} ${num3}`,
      answer: COMPUTE[op2](COMPUTE[op1](num1, num2), num3),
    };
  }
  return {
    question: `${num1} ${op1} (${num2} ${op2} ${num3})`,
    answer: COMPUTE[op1](num1, COMPUTE[op2](num2, num3)),
  };
}