Interesting functions used in an academic functional programming question. Reference for a blog post.

funky_functions.js

function plus_one(x) {
    return x + 1;
}

function twice(f) {
    return function(x) {
        return f(f(x));
    };
}

function n_times(f, n) {
    if (n === 1) {
        return f; 
    } else {
        return function(x) {
            return f((n_times(f, n - 1))(x));
        };
    }
}

function chain(f, n) {
    if (n === 1) {
        return f;
    } else {
        return (chain(f, n - 1))(f);
    }
}