Bucklescript2.md

Bucklescript

Leftovers

Json

use bs-json with it's decoding or external JSON

[@bs.deriving abstract]
type data = {name: string};

[@bs.scope "JSON"] [@bs.val]
external parseIntoMyData : string => data = "parse";

let result = parseIntoMyData("{\"name\": \"Luke\"}");

let n = nameGet(result);

Stringify

Js.Json

Properly use JSON by recursively parse each field

Pipe into variants

let result = name->preprocess->Some

turns into

let result = Some(preprocess(name))

Debug Mode

Printing flags:

NOT FOR PRODUCTION

- `"bsc-flags": ["-bs-g"]` - Pretty print variants, records etc

Composing bs Attributes

bs attributes can be composed

Functions

Modeling a function is like a value. [@bs.val]

Object Method

• bs.send is used to annotate methods on JS objects First argument is always an object

type math; /* abstract type for a document object */
[@bs.val] external math: math = "Math";
[@bs.send] external random: (math, int) => float = "";

let el = random(math, 23);

Methods chaining

bs.send for example exist on JS array so how do we use it with external and chain to filter?

[@bs.send] external map : (array('a), 'a => 'b) => array('b) = "";
[@bs.send] external filter : (array('a), 'a => 'b) => array('b) = "";

let result = [|1, 2, 3|]
  ->map(a => a + 1)
  ->filter(a => a mod 2 === 0);

Fast Pipe

a
->foo(b)
->bar

Variadic Function arguments

Was previously bs.splice. It's used when number of arguments in external function is unknown

[@bs.val] [@bs.scope "global"] [@bs.variadic]
external draw : ([@bs.as "dog"] _, array(int)) => unit = "draw";

draw([|1, 2|]);

Multiple externals

[@bs.module "Drawing"] external drawCat: unit => unit = "draw";
[@bs.module "Drawing"] external drawDog: (~giveName: string) => unit = "draw";
[@bs.module "Drawing"] external draw: (string, ~useRandomAnimal: bool) => unit = "draw";