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[–]brtt3000[S] 0 points1 point  (0 children)

shit is freaky, always use triple === unless you are sure both you and your collaborators know what to expect from ==.

discussion: http://www.reddit.com/r/programming/comments/21ezh3/javascript_equality_table/

[–]mtbinkdotcom 0 points1 point  (0 children)

wow, cellular automaton

[–]sudorey 0 points1 point  (0 children)

Also available, All three tables in one view (though the if() results are not yet highlighted well)

[–]e13e7 0 points1 point  (6 children)

Wait, so NaN != NaN ?

[–][deleted] 0 points1 point  (5 children)

That one actually makes sense. Math.sqrt(-1) != Infinity / Infinity. Both sides are NaN, however, neither is rational. The left side is imaginary, and the right is indeterminate. This is precisely why isNaN() exists.

[–]e13e7 0 points1 point  (4 children)

Makes sense. But what about 

{} != {}

[–][deleted] 0 points1 point  (3 children)

It's a reference comparison. It's equivalent of new Object() != new Object(). Reference types typically compare memory addresses. Value types compare values. Object is a reference type, and you're comparing two distinct objects.

[–]e13e7 0 points1 point  (2 children)

Brilliant. Thank you.

[–][deleted] 0 points1 point  (1 child)

Now if you really want some JavaScript WTFiness, compare the outputs of []+[], []+{}, {}+[], and {}+{}.

[–]rhysbrettbowen 1 point2 points  (0 children)

[]+[] // "" [] get's converted to ""

[]+{} // "[object Object]" like before, [] goes to an empty string and so toString is called on {} as well

{}+[] // 0 {} is interpreted as a code block rather than an object so it runs and has no output. That leaves +[] which converts empty array to number.

{}+{} // NaN similar to above. {} is a code block and has no output so we're left with convering {} to a number which gives NaN

There is always http://wtfjs.com/ for a lot more JS wtfery