illustrating some "dynamic composition" usage

1-utils.js

function flow(...fns) {
	return arg => fns.reduce((res,fn) => fn(res),arg);
}
function partial(fn,initialArgs) {
	return (nextArgs = []) => fn(...initialArgs,...nextArgs);
}
function pick(prop) {
	return obj => obj[prop];	
}
function prepend(prefix) {
	return val => `${prefix}${val}`;
}
function append(suffix) {
	return val => `${val}${suffix}`;
}

// ***************************

function formatName1(name) {
	return `${name.last}, ${name.first}`.toUpperCase();
}
function formatName2(name) {
	const fname = `${name.first}`.toLowerCase();
	return `${fname[0].toUpperCase()}${fname.slice(1)}`;
}

2-dynamic-composition-flow.js

// note: these are partially-applied composition functions
const getCustomerName = partial(flow,[
	pick("customerName"),
	formatName2
]);
const getEmployeeName = partial(flow,[
	pick("employeeName"),
	formatName1
]);

const emailGreeting = record => (
	(record.isEmployee ? getEmployeeName : getCustomerName)
	([
		append("--")
	])
	(record)
);
const chatGreeting = record => (
	(record.isEmployee ? getEmployeeName : getCustomerName)
	([
		prepend("Hello "),
		append("!")	
	])
	(record)
);

3-usage.js

const kyle = { customerName: { first: "Kyle", last: "Simpson", }, };
const sally = { isEmployee: true, employeeName: { first: "Sally", last: "MCDANIELS", }, };

emailGreeting(kyle);          // Kyle--
chatGreeting(kyle);           // Hello Kyle!

emailGreeting(sally);         // MCDANIELS, SALLY--
chatGreeting(sally);          // Hello MCDANIELS, SALLY!

4-dynamic-composition-pipeline.js

// note: these are just arrays
const getCustomerName = [
	pick("customerName"),
	formatName2
];
const getEmployeeName = [
	pick("employeeName"),
	formatName1
];

const emailGreeting = record => (
	record
	|> flow(
			...(record.isEmployee ? getEmployeeName : getCustomerName)
		)(^)
	|> append("--")(^)
);
const chatGreeting = record => (
	record
	|> flow(
			...(record.isEmployee ? getEmployeeName : getCustomerName)
		)(^)
	|> prepend("Hello ")(^)
	|> append("!")(^)
);

5-wishes-pipe-with-spread.js

// note: these are just arrays
const getCustomerName = [
	pick("customerName"),
	formatName2
];
const getEmployeeName = [
	pick("employeeName"),
	formatName1
];

// note: using a proposed `...` extension to `|>`
const emailGreeting = record => (
	record
	|> ...(record.isEmployee ? getEmployeeName : getCustomerName)
	|> append("--")(^)
);
const chatGreeting = record => (
	record
	|> ...(record.isEmployee ? getEmployeeName : getCustomerName)
	|> ...[ prepend("Hello "), append("!") ]
);

6-more-wishes-pipe-arrow.js

// note: these are just arrays
const getCustomerName = [
	pick("customerName"),
	formatName2
];
const getEmployeeName = [
	pick("employeeName"),
	formatName1
];

// note: using a proposed `|=>` which is `|>` + `=>`
const emailGreeting = record |=> (
	...(^.isEmployee ? getEmployeeName : getCustomerName)
	|> append("--")(^)
);
const chatGreeting = record |=> (
	...(^.isEmployee ? getEmployeeName : getCustomerName)
	|> ...[ prepend("Hello "), append("!") ]
);