💾pipe(f, g, ...)

function composition

JS ⟩ value ⟩ function ⟩ higher-order ⟩ example ⟩ pipe()

function composition.

pipe(f, g, h)(x) === h(g(f(x)))
compose(f, g, h)(x) === f(g(h(x)))

💾 程式

• replit ⟩ pipe(f1, f2, ...)

// ⭐ pipe:  
// - pipe(f1, f2, f3 ...)(x,y,z ...) =  ...f3(f2(f1(x,y,z ...)))
//        ╰── funcs ───╯ ╰──args──╯
function pipe(...funcs) {
    return function(...args) {
        return funcs.slice(1).reduce(
            (result, f) => f.call(this, result),  // r = ...f3(f2(r))
            funcs[0].apply(this, args)            // r = f1(x,y,z ...)
        );
    };
}

// ⭐ compose: 
// - compose(f, g, h)(x) = f(g(h(x))) = pipe(h, g, f)(x)
function compose(...funcs) {
    return pipe(...funcs.slice().reverse());
}

• example

const sum = (x, y) => x + y;
const square = x => x * x;
const add3 = x => x + 3;

compose(square, sum)(2, 3)        // 25
pipe(sum, square)(2, 3)           // 25
pipe(sum, square, add3)(2, 3)     // 28

👥 相關

• Boolean

📗 參考

• JavaScript: The Definitive Guide ⟩ 8.8.2 Higher-Order Functions ⭐️

• Eloquent JavaScript ⟩ higher-order functions