chapter_eight.js

//Bugs and Errors

//retry

class MultiplicatorUnitFailure extends Error { }

function primitiveMultiply(a, b) {
  if (Math.random() < 0.2) {
    return a * b;
  } else {
    throw new MultiplicatorUnitFailure("Klunk");
  }
}

function reliableMultiply(a, b) {
  try {
    return primitiveMultiply(a, b);
  } catch (e) {
    if (e instanceof MultiplicatorUnitFailure) {
      return reliableMultiply(a, b);
    } else {
      throw e;
    }
  }
}

console.log(reliableMultiply(8, 8));
// → 64

// the locked box

const box = {
  locked: true,
  unlock() { this.locked = false; },
  lock() { this.locked = true; },
  _content: [],
  get content() {
    if (this.locked) throw new Error("Locked!");
    return this._content;
  }
};

function withBoxUnlocked(body) {
  // Your code here.
  try {
    if (box.locked) {
      box.unlock();
    }
    return body();
  } catch (e) {
    return e.message;
  } finally {
    box.lock();
  }
}

withBoxUnlocked(function () {
  box.content.push("gold piece");
});

try {
  withBoxUnlocked(function () {
    throw new Error("Pirates on the horizon! Abort!");
  });
} catch (e) {
  console.log("Error raised: " + e);
}

console.log(box.locked);
// → true