Pipe & Compose in Javascript #Javascript #fp

compose in Javascript

const compose = (...fns) => {
  return (x) => {
    return fns.reduceRight((v,f) => {
      return f(v)
    }, x)
  }
}

curry function in Javascript

// From Kyle Simpson's works

// The nextCurried function is an immediately invoked function
// The curry function can accept a function and the number of times it is to run as parameters.
function curry(fn, arity= fn.length){
  return (function nextCurried(prevArgs){
    return function curried(nextArg){
      var args = [...prevArgs, nextArg];
      if(args.length >= arity){
        return fn(...args);
      }else{
        return nextCurried(args);
      }
    }
  })([]);
}

//so earlier if the notCurried function accepted 3 params like below,
const notCurried = function(a,b,c){}

//execute the curried function by calling below
const curried = curry(notCurried)(a)(b)

partial Function in Javascript

const testfunction = (x, y) => x + y;

// If y is constant 10
const partialTestFunction10 = testFunction.bind(null, 10);

pipe in Javascript

const pipe = (...fns) => {
  return (x) => {
    return fns.reduce((v,f) => {
      return f(v)
    }, x)
  }
}

Promisified compose in Javascript

// Async compose
const compose = (…functions) => input => functions.reduceRight((chain, func) => chain.then(func), Promise.resolve(input));

// Functions fn1, fn2, fn3 can be standard synchronous functions or return a Promise
compose(fn3, fn2, fn1)(input).then(result => console.log(`Do with the ${result} as you please`))

Promisified pipe in Javascript

const pipe = (…functions) => input => functions.reduce((chain, func) => chain.then(func), Promise.resolve(input));

// Functions fn1, fn2, fn3 can be standard synchronous functions or return a Promise
pipe(fn1, fn2, fn3)(input).then(result => console.log(`Do with the ${result} as you please`))