Simple Functional Programming Examples

Compose

const log = (arg) => {
  console.log(arg);
  return arg;
}
const pipe = (...functions) => (...args) => {
  if (!Array.isArray(functions)) {
    return functions(args);
  }
  else {
    return functions
      .reduceRight(
        (...arguments, f) =>
          Array.isArray(arguments) ?
           f(...arguments) :
           f(arguments)
        , args)
  }
}

const add = (x, y) => x + y;
const double = x => x + x;
const addAndDouble = pipe(double, add);

log(addAndDouble(12, 23));

Pipe

const log = (arg) => {
  console.log(arg);
  return arg;
}
const pipe = (...functions) => (...args) => {
  if (!Array.isArray(functions)) {
    return functions(args);
  }
  else {
    return functions
      .reduce(
        (...arguments, f) =>
          Array.isArray(arguments) ?
           f(...arguments) :
           f(arguments)
        , args)
  }
}

const add = (x, y) => x + y;
const double = x => x + x;
const addAndDouble = pipe(add, double);

log(addAndDouble(12, 23));