Recursive Currying Into Unary Functions

curry.js

function curry(func) {
  const arity = func.length;
  
  function recurry(args=[]) {
    if(args.length == arity) {
      return func(...args); 
    } else {
      return arg => recurry([...args, arg]);
    }
  }
  
  return recurry();
}

example.js

const add = (a, b) => a + b;

const curriedAdd = curry(add);
curriedAdd(3)(5) // -> 8
curriedAdd(3, 3)(5) // -> 8 (extra args are ignored)

const add3 = curriedAdd(3) // -> [Function]
add3(5) // -> 8
add3(5, 6) // - 8 (extra args are ignored)