How to increment an object property value if it exists, else set the initial value?

Question

How might I add check to see if a key already exists, and if does, increment the value, and if it doesn\'t exist, then set the initial value?

Something like this pseudo-

Answer 1

@snak's way is pretty clean and the || operator makes it obvious in terms of readability, so that's good.

For completeness and trivia there's this bitwise way that's pretty slick too:

dict[key] = ~~dict[key] + 1;

This works because ~~ will turn many non-number things into 0 after coercing to Number. I know that's not a very complete explanation, but here are the outputs you can expect for some different scenarios:

~~(null)
0
~~(undefined)
0
~~(7)
7
~~({})
0
~~("15")
15