Compose
What is compose
Compose is a system design principle that allows us to dynamically comibine serveral funcions and returns the resut.
Example without compose
// data -> fn -> data -> fn -> data
const add1 = (n) => n + 1;
const multiplyBy5 = (n) => n * 5;
const minus10 = (n) => n - 10;
const calculate = (n) => {
const a = add1(n);
const b = multiplyBy5(a);
const c = minus10(b);
return c;
};
const result = calculate(2);But we now can do it by composing these three functions, like this:
Example with compose
const composeResult = compose(minus10, multiplyBy5, add1)(2);
const pipeResult = pipe(add1, multiplyBy5, minus10)(2);Implementation
const composeReducer = (fn1, fn2) => (...args) => fn1(fn2(...args));
const pipeReducer = (fn1, fn2) => (...args) => fn2(fn1(...args));
const compose = (...fns) => fns.reduce(composeReducer);
const pipe = (...fns) => fns.reduce(pipeReducer);
//compose
// (...args) => minus10(multiplyBy5(...args)) --->acc
// (...args) => acc(add1(…args)) --->acc
//pipe
// (...args) => multiplyBy5(add1(...args)) --->acc
// (...args) => minus10(acc(...args)) --->acc