Look on my works, ye Mighty, and despair!

Currying and partial function application are two concepts from functional programming that sound far more complicated than they really are.

One of the times I find myself wishing it were more convenient to do in JavaScript is when trying to escape callback hell by extracting functions:

var shared = new Shared();
doSomething(shared).then(function(result) {
    somethingElse(shared, result);
});

It would be nice to be able to go straight to this:

var shared = new Shared();
doSomething(shared).then(somethingElse);

Of course this wouldn’t work, as the somethingElse function expects 2 parameters instead of just one.

If JavaScript supported partial application in the way that the ML family of languages do, then we could say:

doSomething(shared).then(somethingElse(shared));

But that means something entirely different in JavaScript: the result of the function being executed with one argument would be passed in.

It’s relatively straightforward to write a curry function and use that, but there is an alternative; returning an appropriate function from the called method:

var shared = new Shared();
doSomething(shared).then(somethingElse(shared));

function somethingElse(shared, result) {
    return function(result) {
        // do something with shared & result
    };
}