Comparing NaN values for equality in Javascript

Question

I need to compare two numeric values for equality in Javascript. The values may be NaN as well. I\'ve come up with this code:

if (val1 == val2 |         


        

Answer 1

Avoid isNaN. Its behaviour is misleading:

isNaN(undefined) // true

_.isNaN (from Underscore.js) is an elegant function which behaves as expected:

// Is the given value `NaN`?
// 
// `NaN` is the only value for which `===` is not reflexive.
_.isNaN = function(obj) {
  return obj !== obj;
};

_.isNaN(undefined) // false
_.isNaN(0/0) // true