caasi

const ZERO = 'a'.charCodeAt(0);
const WIDTH = 5;

const f = Math.floor;

function vPath(n: number): string {
  if (n === 0) return '';
  if (n > 0) return 'D'.repeat(n);
  if (n < 0) return 'U'.repeat(-n);
  return '' as never;

caasi

import { useState, useMemo, useEffect } from 'react';
import { Observable, BehaviorSubject } from 'rxjs';

// It's like the `useObservable` from 'rxjs-hooks' but with a better interface.
function useObservable<State>(
  input$: Observable<State>,
  initialState?: State,
) {
  const [state, setState] = useState(initialState);
  const state$ = useMemo(() => new BehaviorSubject(initialState), []);

caasi

import { of } from 'rxjs';
import { flatMap, tap } from 'rxjs/operators';

describe('containers', () => {
  it('promise works', () => {
    const c =
      Promise.resolve(1).then(a =>
        Promise.resolve(2).then(b =>
          a + b
        )

caasi

type Foo = 0 & { readonly brand?: unique symbol };
type Bar = 1 & { readonly brand?: unique symbol };
type Baz = 0 & { readonly brand?: unique symbol };

type Foobar = Foo | Bar;

const Foobar = {
    FOO: 0 as Foo,
    BAR: 1 as Bar,
};

caasi

open Webapi.Dom;
open Webapi.Canvas;
open HtmlImageElement;

module MyCanvas2d = {
  include Canvas2d;
  [@bs.send.pipe : Canvas2d.t] external drawImage : (HtmlImageElement.t, float, float) => unit = "drawImage";
}

let useImageData = url => {

caasi

type ICallback = (i: number) => string

class Foo {
  cb: ICallback = () => ''
  registerCb(cb: ICallback) {
    this.cb = cb
  }
}

const foo = new Foo()

caasi

// Some helper types from:
// https://dev.to/miracleblue/how-2-typescript-get-the-last-item-type-from-a-tuple-of-types-3fh3

// Borrowed from SimplyTyped:
type Prev<T extends number> = [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62][T];

// Actual, legit sorcery
// Borrowed from pelotom/hkts:
type GetLength<original extends any[]> = original extends { length: infer L } ? L : never;
type GetLast<original extends any[]> = original[Prev<GetLength<original>>];

caasi

const xs = [1, 3, 5, 8, 9];

let sum = 0;
for (let i = 0; i < xs.length; ++i) {
    sum += xs[i];
}
console.log(sum);

let sum2 = 0;
for (let key in xs) {

caasi

success = (f) -> f undefined, 1
failure = (f) -> f new Error('oops')

err, value <- success
console.error err if err
console.log value
err, value <- failure
console.error err if err

caasi

foo(0, 1, 2, function(x) {
  return bar(0, 1, function(y) {
    return x + y;
  });
});

// v.s.

foo(0, 1, 2, (x) =>
bar(0, 1, (y) =>