babel-plugin-functional-composition

Functional Composition

Babel plugin for functional code bases

Get it

npm install --save-dev babel-plugin-functional-composition

Use it

// .babelrc
{
  "plugins": ["functional-composition", {
    "name": "pipe" // optional - defaults to `pipe`
    "as": "pipe" // optional - defaults to `pipe`
    "from": "ramda" // optional, but required for automatic imports
  }]
}

Left to right composition >>

const add3 = x => x + 3
const add2 = x => x + 2

const y = add2 >> add3
// will become
const y = pipe(add2, add3)

Right to left composition <<

const add3 = x => x + 3
const add2 = x => x + 2

const y = add2 << add3
// will become
const y = pipe(add3, add2)

Both directions of Composition

const add3 = x => x + 3
const add2 = x => x + 2
const add1 = x => x + 1

const y = add2 >> add3 << add1
// will become
const y = pipe(add1, pipe(add2, add3))

>>> For non-curried functions

Suppose you have a functional API that is not curried you can now do this. >>> will place the left expression as the last parameter to the right expression.

import { map, from, scan } from 'most'

const add1 = x => x + 1

const x = from([1, 2, 3]) >>> map(add1) >>> scan(add1, 0)
// will become
const x = scan(add1, 0, map(add1, from([1, 2, 3])))

const y = 3 >>> add1
// will become
const y = add1(3)

This plugin is opt-in only - use fc

By default >>, <<, and >>> will do nothing for you that JS does not already do, because in order to activate these features a directive must be applied.

3 >>> 3 // still a bitwise operation

const add1 = x => x + 1

function add1To (x) {
  'use fc' // activates plugin in this scope

  return x >>> add1 // becomes add1(x)
}

Notes about the options object

If the (optional) options object is provided, with at the minimum from, if the import does not exist yet, the import will be added for you. This is useful for things like eslint complaining about unused imports. name is the the part of the object that you would normally import e.g. pipe in import { pipe } from 'ramda'. If name is not the name you'd like to have imported as, perhaps it conflicts with another import, you can specify as to import it as something else. import { pipe as sequence } from 'ramda', will be added to your files if the as option is provided.

So for instance if your are using ramda all you will need is

{
  "plugins": [
    ["functional-composition", { "from": "ramda" }]
  ]
}

and at the top of your file this plugin will add import { pipe } from 'ramda' for you.