partialCurried.js

const map = fn => array => array.map(fn);
const multiply = x => y => x * y;
const pluck = key => object => object[key];

const discount = multiply(0.98);
const tax = multiply(1.0925);

const custReq = request({
	headers: { 'X-Custom': 'mykey' }
});

// 3 iterations
customReq({ url: '/cart/items' })
	.then(map(pluck('price')))
	.then(map(discount))
	.then(map(tax));

// with composition...1 iteration
customReq({ url: '/cart/items' })
	.then(map(
		compose(
			tax, 		   // 3
			discount,	   // 2
			pluck('price') // 1
		)
	));