Truthiness

Javascript (and other languages) have something called Truthiness. Ok, it's actually called Truthy or Falsy. It is the idea that we can infer something is true, similar to assuming.

Falsy

If something does not exist (like NaN) or has a value equating to zero, it is considered false. For example, an empty string of "" would be considered false. It has no value.

Truthy

If the data has value (other than specifically NaN, zero, or false) it is considered true, because it has value. For example, 1 == '1' will result in true because they are equal in value (Javascript converts on-the-fly). However, 1 === '1' will return false because they are not exactly equal (one is a numeric value, the other a string).

NaN stands for Not a Number. Think of it like "undefined" or "does not exist". Note: division by zero gives an answer of infinity.