Function Currying

What will this function return?

const compose = (f, g) => (x) => f(g(x));
const addOne = (x) => x + 1;
const double = (x) => x * 2;

const addOneThenDouble = compose(double, addOne);
const result = addOneThenDouble(3);

7
8
The function will return 8. This example demonstrates function composition, a technique closely related to currying. The `compose` function takes two functions and returns a new function that applies the first function to the result of applying the second function to its argument. Here's the evaluation step by step: `addOneThenDouble(3)` calls `double(addOne(3))`, which is `double(4)`, which equals `8`. Function composition is powerful for building complex transformations from simpler ones, and currying makes functions more composable by standardizing them to take one argument at a time. This is a foundational pattern in functional programming.
9
10

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