JavaScript function composition

JavaScript function composition: What’s the big deal? by James Sinclair

// We call our function c2, short for 'compose two functions together'. 

const c2 = (funcA, funcB) => x => funcA(funcB(x));

const compose = (...fns) => x0 => fns.reduceRight( (x, f) => f(x), x0 );

// We call this function 'flow' as the values flow, from left to right.
const flow = (...fns) => x0 => fns.reduce( (x, f) => f(x), x0 );

const pipe = (x0, ...fns) => fns.reduce( (x, f) => f(x), x0 );

const map = f => function*(iterable) { 

   for (let x of iterable) yield f(x); 

}; 

const filter = p => function*(iterable) { 

   for (let x of iterable) { 

       if (p(x)) yield x; 

   } 

}; 

const take = n => function*(iterable) { 

    let i = 0; 

    for (let x of iterable) { 

        if (i >= n) return; 

        yield x; 

        i++; 

    } 

}; 

const join = s => iterable => [...iterable].join(s);