confused with teachers note ?

Hi Vikrant. isNan() is a Javascript function that tells you if something is NOT a number. If you pass it a number it will return false because a number is "not" not a number. If you pass it a string or anything other type it will return true because strings and other types are not numbers.

aNumber = isNan(6);
aNumber = isNan("Vikrant")

In the first example aNumber will equal false because 6 is a number (or "not" not a number) In the second example aNumber will equal true because "Vikrant" is a string not a number.

In the video Guil uses parseInt to convert the string to an int. parseInt will return the integer number or NaN if its not a number. The if statement uses the value returned from parseInt. So its going to be a number or NaN if its not a number. Any value 1 or greater will evaluate to true in the if statement and NaN will evaulate to false. So "if(1)" would be true. The problem is if zero is entered the if statement will fail like its not a number because zero is evaluated to false.

So in the teachers note they use the isNaN function to check:

if ( isNaN(lowNumber) || isNaN(highNumber) ) {
  console.log('You need to provide two numbers. Try again.');
} else { .......

}

so in plain English this say "if lowNumber is not a number OR highNumber is not a number THEN tell the user 'You need to provide two numbers. Try again.' "

Hope this helps make it less confusing.

Thank you that explains it better but guil had did nan then passed a number is was true I was just in general confused with video, the explanation does help a little