#javascript

All the things that are falsy, including an array with one item that is falsy itself, which gets recursive.

Some other weird things about falsy Javascript:

false == false
0 == false
[] == false
"" == false
"0" == false
"\t" == false
[] == false
["0"] == false
[[["0"]]] == false
[[[1 - 1]]] == false
[[[{}.foobar]]] == false
[[[`\t ${[].length} \t`]]] == false

// BUT

[false] != false

So, yesterday I learned that [] == [] is false in Javascript. Today my adventures with arrays lead me to this:

const coffees = ['espresso', 'latte', 'filter']
console.log(
  'filter' in coffees,
  'cappuchino' in coffees,
  'espresso' in coffees
)

// => true, false, false

Oh Javascript.