How do I check if a number evaluates to infinity?

Question

I have a series of Javascript calculations that (only under IE) show Infinity depending on user choices.

How does one stop the word Infinity appearing a

Answer 1

I've ran into a scenario that required me to check if the value is of the NaN or Infinity type but pass strings as valid results. Because many text strings will produce false-positive NaN, I've made a simple solution to circumvent that:

  const testInput = input => input + "" === "NaN" || input + "" === "Infinity";

The above code converts values to strings and checks whether they are strictly equal to NaN or Infinity (you'll need to add another case for negative infinity).

So:

testInput(1/0); // true
testInput(parseInt("String")); // true
testInput("String"); // false