Compose

compose.js

const add = (a, b) => a + b;
const add10 = num => add(num, 10);
const add200 = num => add(num, 200);
const addNew = a => b => a + b;

console.log(add(10, 20))    // 30
console.log(add10(10))      // 20
console.log(addNew(10)(20)) // 30
console.log(add200(10))     // 210


const compose = (...args) => target => {
  return args.reduceRight((previousFn, currentFn) => {
    return currentFn(previousFn);
  }, target);
};

console.log('output',
  compose(
  add10,
  add200,
  add200
  )(0)
) // 410

const addProps = props => obj => {
  return Object.assign({}, obj, props)
};

const deleteProps = props => obj => {
  const objCopy = Object.assign({}, obj); 
  props.forEach(prop => {
    delete objCopy[prop]
  });
  return objCopy;
};

console.log('output',
  compose(
  addProps({qux: true}),
  addProps({baz: true}),
  deleteProps(['foo', 'bit']),
  addProps({bar: true}),
  addProps({bit: true}),
  )({
    foo: true
  })
) // { bar: true, baz: true, qux: true }