Well usually it would be for something that is useful, like

const greaterThan = x => y => y > x

and then I can do thins like

numbers.filter(greaterThan(10))

because greatherThan(10) is a function (and I hope I did put the correct comparison operator :)

It also works better on languages using free functions than those using method calls e.g. in Haskell you have

    filter :: (a -> Bool) -> [a] -> [a]

so you partially apply to a predicate to get a specific filter condition which you can apply to various contexts e.g.

    over10 = filter (>= 10)

That's why functional languages tend to put the callback first in HoFs, it's usually the more common partial application case.

You can not use partial application with that. for example const add = x=>y=>x+y

can be partialy applied like the following const add3 = add(3) // this is also a function

> You can not use partial application with that.

You can:

    const add3 = add.bind(null, 3)

I still like currying better, but I just might be weird like that :-)

I only asserted that you could partially apply regular functions. But I don't think currying looks or feels nice in Javascript.

Proper curried languages are definitely better suited for partial application though.

You could use default parameters in this case.

const add = (a, b=0) => {return a+b}