Why does the console show "undefined"?

JavaScript
1

I’m doing a tutorial from FreeCodeCamp and learning JS. I’m doing a section on anonyous functions. I’m using the website runjs dot app to test and run Javascript. When I do this code:

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];
const squareList = (arr) => {
  const squaredIntegers = arr.filter(num => Number.isInteger(num) && num > 0);
  //Get squre of only positive integers in arr.
  //First remove numbers < 0.
  
  return squaredIntegers;
};
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);

The console shows me the correct array but on the next line it says “undefined.” Why does the undefined show in the console?

[ 4, 42, 6 ]
undefined

Could this be a quirk of the runjs.app website?

Thank you.

3

the undefined is the output of theconsole.log, in this environment you don’t need to use console.log to see the output, as the output of the last line is printed automatically. You would see the same behaviour using the browser console