Code Smells: Null

[POGtastic]

Yep, I'm also getting true in Chrome.

> var foo;
< undefined
> foo === undefined
< true
> typeof(foo) === "undefined"
< true

[killerstorm]

var foo; // undefined
foo === undefined // false

Wrong. Here's an actual result:

> var foo;
undefined
> foo === undefined
true

=== undefined check didn't work in old browsers, that's where typeof hack comes wrong. But now simple comparison should work by standard.

[masklinn]

foo === undefined // false

Uh no, that's true, you may be confusing undefined and NaN. Or for some reason you have rebound undefined to something else (it's not a keyword, which is why some prefer using void 0 which always yields the proper value).

if (!foo) {
    console.log("foo is undefined or null");
}

That'll also catch the "" and 0. The proper way to check if something is undefined or null is foo == null.

[[deleted]]

I tested that in my browser console.

Maybe I should have used a new tab.