react-maths-app/utils.js at main · slothmock/react-maths-app · GitHub

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const operators = ['+', '-', '*', '/'];

export const generateQuestion = () => {
  const op = operators[Math.floor(Math.random() * operators.length)];
  let num1, num2, correct;

  switch (op) {
    case '+':
      num1 = Math.floor(Math.random() * 10);
      num2 = Math.floor(Math.random() * 10);
      correct = num1 + num2;
      break;
    case '-':
      num1 = Math.floor(Math.random() * 10);
      num2 = Math.floor(Math.random() * num1); // ensures non-negative
      correct = num1 - num2;
      break;
    case '*':
      num1 = Math.floor(Math.random() * 10);
      num2 = Math.floor(Math.random() * 10);
      correct = num1 * num2;
      break;
    case '/':
      num2 = Math.floor(Math.random() * 9) + 1;
      correct = Math.floor(Math.random() * 10);
      num1 = num2 * correct; // ensures whole number division
      break;
  }

  const displayOp = op === '*' ? '×' : op === '/' ? '÷' : op;

  const choices = [
    correct,
    correct + 1,
    correct - 1,
    correct + 2,
  ].sort(() => Math.random() - 0.5);

  return { num1, num2, op, displayOp, correct, choices };
};