'X is not defined' error

JavaScript
1

I’m doing the ES6 JS challenges and I’m at the “Higher Order Arrow Functions” challenge. The code I’m using to solve this is:

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];

const squareList = (arr) => {
  "use strict";
  // This is my solution
  const squaredIntegers = (arr.filter(x => x > 0 && x % parseInt(x) === 0)).map(x => x*x);
  // End of solution
  return squaredIntegers;
};
// test your code
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);

But it prints a message saying ‘x is not defined’, even though I saw that the MDN docs had similar usage and did not define variables in anonymous functions… What’s the right way to define these variables then? I know I can solve this by defining x using let/var in the function scope of squareList, but then how is MDN showing examples which are innacurate?

2

Hello check, array.prototype.filter(). in you case it is (arr.filter).

Hope this hint helps to solve it.

3

There’s nothing wrong with the code you wrote. Try clearing your browser cache - the tests run fine for me.

Note you don’t need the extra set of parentheses around the filter function - it won’t do anything bad, you’re just telling JS to execute something, which it is already doing anyway.

4

I figured out the problem, since 'use strict' is given, I can’t use undefined variables in the code. Whereas the MDN Docs did not have this directive in their example code, so they got away without defining their in-function use of x.

5

You don’t have any undefined variables and neither do MDN, it has nothing to do with that.

6

Well, removing the ‘use strict’ directive solved the problem so I don’t know what else could be happening.

7

What browser are you using?

9

I’m using Chrome, the latest version (69+). However, the issue is not with my code, but with the cache or something as DanCouper suggested. I reset the challenge and it now works without modification to the ‘use strict’ directive. Seems to be a fluke or some sort.