On: NPM Vulnerability Discussion on Twitter

[onion2k]

How do you handle someone inputting undefined/null/a string/a random object/NaN/etc?

Your isEven function should check that it's operating on a number. Eg "const isEven = (i) => typeof i === 'number' && i % 2===0;" If it's not a number then calling isEven on it doesn't make sense. If the user wants to check if a string is even then they can convert it before making the call.

[kuschku → onion2k]

Now someone is going to define const isOdd = (i) => !isEven(i); and you’ll get trouble.

A proper solution would be along the lines of:

    const isRealNumber = (n) => {
      if (typeof n !== 'number') return false;
      if (isNaN(n)) return false;
      if (n === +Inf || n === -Inf) return false;
      return true;
    };

    const isEven = (n) => {
      if (!isNumber(n)) throw new Error("Numerical error: Invalid input");
      return n % 2 === 0;
    }

    const isOdd = (n) => {
      if (!isNumber(n)) throw new Error("Numerical error: Invalid input");
      return n % 2 !== 0;
    }

This is the additional complexity created by dynamically weakly typed languages. And that’s why we get all these BS tiny npm packages.

[jasonlotito → onion2k]

The irony of using the isEven as an example of what you should just write yourself and then providing an example that returns a truthy value for isEven(3).

[onion2k → jasonlotito]

No idea what you mean. ;)