Object.is

Until now, most people used either the equals (==) or the identically equals (===) operator to compare two values. The latest was the recommended way to test for identity since it avoids performing type coercion during the comparison. Unfortunately, even the identity equals operator isn’t entirely accurate. Here’s an example:

+0 === –0 //returns true
NaN === NaN //returns false

Fortunately for us, the latest release of the spec introduces the Object.is method, which takes care of the quirks associated with the use of the equal operators. It accepts 2 arguments and returns true when those values are equivalent. Btw, equivalent here means that the values have the same type and the same value. Here’s how to get the correct results for the previous example:

Object.is( +0, –0); //false
Object.is( NaN, NaN); //true

Bottom line: Object.is produces the result that the identity equals operator should have produced for all the existing values and you should use it when writing JavaScript 6 code.