如果 ReasonML 没有 JavaScript 的那些怪癖，你该不该试试它？

ReasonMLlet a = "Hi";TypeScriptconst a = "Hi"

let sum = (a: number, b: number) => a + b

let sum = (a,b) => a + b;

let sum = (a: int, b: int) => a + b;

TypeScriptinterface Product {  name: string  id: number}

type product = {  name: string,  id: int,};

let formatName = product => "Name: "++product.name;

const formatName = (product: Product) => "Name: " + product.name

let updateName = (product, name) => { ...product, name };

const updateName = (product: Product, name: string) => ({ ...product, name })

function updateName(product, name) {  return [name, product[1]]}

interface State {  movies: string[]}
const defaultState: State = {  movies: [],}
export const ADD_MOVIE = "ADD_MOVIE"export const REMOVE_MOVIE = "REMOVE_MOVIE"export const RESET = "RESET"
interface AddMovieAction {  type: typeof ADD_MOVIE  payload: string}
interface RemoveMovieAction {  type: typeof REMOVE_MOVIE  payload: string}
interface ResetAction {  type: typeof RESET}
type ActionTypes = AddMovieAction | RemoveMovieAction | ResetAction
export function addMovie(movie: string): ActionTypes {  return {    type: ADD_MOVIE,    payload: movie,  }}
export function removeMovie(movie: string): ActionTypes {  return {    type: REMOVE_MOVIE,    payload: movie,  }}
export function reset(): ActionTypes {  return {    type: RESET,  }}
const reducer = (state: State, action: Action) => {  switch (action.type) {    case ADD_MOVIE:      return { movies: [movie, ...state.movies] }    case REMOVE_MOVIE:      return { movies: state.movie.filter(m => m !== movie) }    case RESET:      return defaultState    default:      return state  }}

type state = {  movies: list(string)};
type action =  | AddMovie(string)  | RemoveMovie(string)  | Reset
let defaultState = { movies: [] }
let reducer = (state) => fun  | AddMovie(movie) => { movies: [movie, ...state.movies] }  | RemoveMovie(movie) => { movies: state.movies |> List.filter(m => m !== movie) }  | Reset => defaultState;
/* No need for additional functions! */let someAction = AddMovie("The End of Evangelion")

type action =  | AddMovie(string)  | RemoveMovie(string)  | Reset

let reducer = (state) => fun  | AddMovie(movie) => { movies: [movie, ...state.movies] }  | RemoveMovie(movie) => { movies: state.movies |> List.filter(m => m !== movie) }  | Reset => defaultState;

let reducer = (state, action) => {  switch(action) {  | AddMovie(movie) => { movies: [movie, ...state.movies] }  | RemoveMovie(movie) => { movies: state.movies |> List.filter(m => m !== movie) }  | Reset => defaultState;  }}

Warning 8: this pattern-matching is not exhaustive.Here is an example of a case that is not matched:Sort

type option('a) =  | Some('a)  | None;

interface User {  phone?: number}
interface Form {  user?: User}
function getPhone(form: Form): number | undefined {  if (form.user === undefined) {    return undefined  }  if (form.user.phone === undefined) {    return undefined  }  return form.user.phone}

open Belt.Option;
type user = {  phone: option(int)};
type form = {  user: option(user)};
let getPhone = form =>  form.user->flatMap(u => u.phone);

function makeShadow(x: number, y: number, spread: number, color: string) {  return 0}const shadow = makeShadow(10, 10, 5, "black") /* meh */

let makeShadow = (~x: int, ~y: int, ~spread: int, ~color: string) => {  0;}
let shadow = makeShadow(~spread=5, ~x=10, ~y=10, ~color="black")

function makeShadow(args: {  x: number  y: number  spread: number  color: number}) {  return 0}
const shadow = makeShadow({ x: 10, y: 10, spread: 5, color: "black" })

export const test = "Hello"

import { test } from "./Hello.ts"
console.log(test)

let test = "Hello";

Js.log(Hello.test);

open Hello;
Js.log(test);

$ time tsc -p jstsc -p js 6.18s user 0.24s system 115% cpu 5.572 total

$ bsb -clean-world$ time bsb -make-world[18/18] Building src/ReactDOMRe.mlast.d[9/9] Building src/ReactDOMRe.cmj[6/6] Building src/Fetch.mlast.d[3/3] Building src/bs_fetch.cmj[12/12] Building src/Json_encode.mlast.d[6/6] Building src/Json.cmj[7/7] Building src/todomvc/App.mlast.d[3/3] Building src/todomvc/App-ReasonReactExample.cmjbsb -make-world 0.96s user 0.73s system 161% cpu 1.049 total

$ bsb -clean$ time bsb -make-worldninja: no work to do.ninja: no work to do.ninja: no work to do.[7/7] Building src/todomvc/App.mlast.d[3/3] Building src/todomvc/App-ReasonReactExample.cmjbsb -make-world 0.33s user 0.27s system 117% cpu 0.512 total