XReact Fantasy

xReact is a Functional library that can integrate FRP lib rxjs or mostjs into react. But there’re still too many verbose you need to care while modeling UI components.

The implement of Fantasy Land, which will change the way you model and implement UI entirely.

The idea of FantasyX is highly inspired by flare by purescript


Let’s use List as example, what lift does is very similar to map

const f = x => x + 1
[1,2,3].map(f) // => [2,3,4]

It simply map f to every items in the list. While if we do it another way around:

const lf = lift(f)
lf([1,2,3]) // => [2,3,4]

Now lf can take a list, apply f to each item, and return a new list. So lf is just a lifted version of f. You should notice that both lift and map transform x => x + 1 which should only able to apply to Number, to a function that can apply to Array<Number>

We can now (from v2.3.0) lift a normal function(takes value and return value) to a FantasyX level function(take FantasyX and return FantasyX) as well.

Let’s take a look at a really simple example, multiply 2 numbers.

// Number -> Number -> Number
function mult(a, b) {
  return a * b
mult(1, 2)

But if we need a React Component that multiply 2 numbers from 2 input boxes, how complicated it could be?

Now you get simply get a free FantasyX from just any normal function, via lift.

// FantasyX -> FantasyX -> FantasyX
let xMult = lift2(mult)

mult need 2 arguments, that’s why we use lift2 here.

Now that we have on function xMult that can turn 2 FantasyX into one, lets do this:

let XMult = xMult(xinput('a'), xinput('b'))

and we got a new FantasyX XMult with the computation built in.

xinput is an FantasyX abstraction of input box.

All we have so far was just a FantasyX XMult with computation composed inside, and we need a View to display and interact with. Here comes a really simple Stateless Component

const View = props => (
    <input name="a" onChange={props.actions.fromEvent} defaultValue={props.a}/>
    <input name="b" onChange={props.actions.fromEvent} defaultValue={props.b}/>
View.defaultProps = { a: "", b: "",output:""}

apply XMult to View then we’ll get a React Component

let Mult = XMult.apply(View)



FantasyX also implemented Functor, so we can transform one FantasyX to another

For example, from XMult, we could simply transform it into a XMMP with new computation

let XMMP = XMult.map((s) => ({output: s.output * s.output}))

it’s just like mapping on a list

// [2,4,6]



It’s actually Semigroup, but if we have a ID FantasyX, we have Monoid, an Identity FantasyX make sense in that the computation inside is just Identity.

Anyway, let’s see how can we combine two FantasyX together

let XCOMBINE = XMMP.concat(XMult)

仅此, 我们就得到了一个同时具有 XMMP 与 XMult 行为的 FantasyX

当然, 因为他们都会修改 state.output, 合并到一起会导致冲突, 我们稍微修改下 XMMP

let XMMP = XMult.map((s) => ({output2: s.output * s.output}))

nothing special just like how you concat two Arrays


Check out a more complicated BMI Calculator: