It turns out +0 === -0 evaluates to true despite +0 and -0 being different entities. So, how do you differentiate +0 from -0?
+0 === -0
true
+0
-0
There is a hack:
if (1 / myZero > 0) { // myZero is +0 } else { // myZero is -0 }
Can I do better?
In ECMAScript 6 Object.is behaves like === except that it distinguishes positive and negative zeroes, and Object.is(NaN, NaN) evaluates to true. (See here for a writeup.)
Object.is
===
Object.is(NaN, NaN)
Chrome 24 supports Object.is.
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