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JavaScript developer friendly syntax

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let meaningOfLife = 41 + 1;

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let add = (x, y) => x + y; add(2, 2); add(41, 1);

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let fruits = ["Apple", "Orange"];

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if (true) { print_string("Hello World!"); };

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OCaml semantics

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Reason Syntax OCaml Syntax OCaml AST

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Records

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let jane = {name: "Jane", age: 40};

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let jane = {name: "Jane", age: 40};

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type person = { name: string, age: int, }; let jane = {name: "Jane", age: 40};

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type person = { name: string, age: int, }; let jane = {name: "Jane", age: 40}; let tim = {...jane, name: "Tim"};

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Compiles to JavaScript

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Reason Syntax OCaml Syntax OCaml AST JavaScript BuckleScript

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Reason Syntax OCaml Syntax OCaml AST Native Code JavaScript BuckleScript

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Fromatter

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Reason Syntax OCaml Syntax OCaml AST Native Code JavaScript BuckleScript

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Reason Syntax OCaml Syntax OCaml AST Native Code JavaScript refmt BuckleScript

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Statically Typed Language

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Why yet another one?

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const pieces = [ { kind: "king", color: "black", position: [3, 4] }, { kind: "pawn", color: "black", position: [4, 2] }, { kind: "knight", color: "white", position: [3, 3] } ]; JavaScript

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interface Piece { kind: string; color: string; position: number[]; } const pieces = [ { kind: "king", color: "black", position: [3, 4] }, { kind: "pawn", color: "black", position: [4, 2] }, { kind: "knight", color: "white", position: [3, 3] } ]; const getKinds = (pieces: Piece[]) => pieces.map(piece => piece.kind); TypeScript

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type piece = { kind: string, color: string, position: (int, int), }; let pieces = [ {kind: "king", color: "black", position: (3, 4)}, {kind: "pawn", color: "black", position: (4, 2)}, {kind: "knight", color: "white", position: (3, 3)}, ]; let getKinds = pieces => List.map(item => item.kind, pieces); Reason

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Variants

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type direction = | Up | Down | Left | Right;

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type direction = | Up | Down | Left | Right; let move = Left;

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type direction = | Up(int) | Down(int) | Left(int) | Right(int); let move = Left(2);

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type data = {names: list(string)}; type request = | Loading | Error(int) | Success(data);

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type color = Black | White; type kind = Queen | King | Rook | Bishop | Knight | Pawn; type piece = { color, kind, position: (int, int), }; let pieces = [ {kind: King, color: Black, position: (3, 4)}, {kind: Pawn, color: Black, position: (4, 2)}, {kind: Knight, color: White, position: (3, 3)}, ];

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Pattern Matching

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switch () { | => | => | ... };

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switch (1) { | 0 => "off" | 1 => "on" | _ => "off" };

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let displayText = switch (1) { | 0 => "off" | 1 => "on" | _ => "off" };

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type data = {names: list(string)}; type request = | Loading | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };

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type data = {names: list(string)}; type request = | Loading | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(401) => "You aren’t authenticated." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };

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type data = {names: list(string)}; type request = | Loading | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(401 | 402) => "You aren’t authenticated." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };

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– Tony Hoare “I call it my billion-dollar mistake …”

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Lesson I Don’t implement anything just because it’s easy!

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Lesson II Null is BAD!

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null; // doesn't exist!

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Option

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let foo = None; let foo = Some(42); let foo = Some([1, 2, 3]); let foo = Some("Hello World!");

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let foo = None; let foo = Some(42); let foo = Some([1, 2, 3]); let foo = Some("Hello World!"); switch (foo) { | None => "Sadly I don't know." | Some(value) => "It's " ++ value };

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Functions

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let add = (x, y) => x + y; add(2, 2); add(41, 1);

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let name = (~firstName, ~lastName) => firstName ++ " " ++ lastName; /* Jane Doe */ name(~firstName="Jane", ~lastName="Doe"); /* Jane Doe */ name(~lastName="Doe", ~firstName="Jane");

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ReasonReact

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Stateless Component let component = ReasonReact.statelessComponent("Greeting"); let make = (_children) => { ...component, render: _self =>

(ReasonReact.string("Hello"))

, }; ReactDOMRe.renderToElementWithId(, "root"); Greeting.re App.re

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Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children) => { ...component, render: _self =>

(ReasonReact.string(“Hello " ++ name))

, }; ReactDOMRe.renderToElementWithId(, "root"); Greeting.re App.re

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Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children) => { ...component, render: _self =>

(ReasonReact.string("Hello " ++ name))

, }; ReactDOMRe.renderToElementWithId(, "root"); Greeting.re App.re

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Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children) => { ...component, render: _self =>

(ReasonReact.string("Hello " ++ name))

, }; ReactDOMRe.renderToElementWithId(, "root"); Greeting.re App.re

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type state = {count: int};

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type state = {count: int}; type action = | Add(int) | Reset;

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type state = {count: int}; type action = | Add(int) | Reset; let s = ReasonReact.string;

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type state = {count: int}; type action = | Add(int) | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter");

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type state = {count: int}; type action = | Add(int) | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make = _children => { ...component, initialState: () => {count: 0}, reducer: (action, state) => switch (action) { | Add(value) => ReasonReact.Update({count: state.count + value}) | Reset => ReasonReact.Update({count: 0}) },

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(s(string_of_int(self.state.count)))

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let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make = _children => { ...component, initialState: () => {count: 0}, reducer: (action, state) => switch (action) { | Add(value) => ReasonReact.Update({count: state.count + value}) | Reset => ReasonReact.Update({count: 0}) }, render: self =>

(s(string_of_int(self.state.count))) self.send(Add(1)))> (s(“Add")) self.send(Add(2)))> (s("Add 2")) self.send(Reset))> (s("Reset"))

, };

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Manage your State with GraphQL

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Interop with JavaScript

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BuckleScript allows us to write bindings ReasonReact - wrapJsForReason - wrapReasonForJs

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[@bs.module "rebass"] external jsArrow : ReasonReact.reactClass = "Arrow"; let make = (~direction: string, children) => ReasonReact.wrapJsForReason( ~reactClass=jsArrow, ~props={"direction": direction}, children, );

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Variants to the rescue!

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[@bs.module "rebass"] external jsArrow : ReasonReact.reactClass = "Arrow"; type direction = | Up | Down; let make = (~direction, children) => { let directionString = switch (direction) { | Up => "up" | Down => "down" }; ReasonReact.wrapJsForReason( ~reactClass=jsArrow, ~props={"direction": directionString}, children, ); };