Deno and Abc

September 23rd, 2020 By Alex Hu

I want to enhance my existing Android video player app to support streaming files, and also create a new mobile app as my very own personal assistant. They are going to access a local private server to run some operations on my main computer.

Although I can add additional API into the existing Portfolio Next.js app, I decided on the a different server app since this local server is going to be run on my computer at home instead of published in the web.

Deno

Deno is a simple, modern and secure runtime for JavaScript and TypeScript that uses V8. I very much prefer the async / await that it offers. Not to mention that it is new and shiny. However, like most new framework, it is less refine. For example, it takes some workaround to get Ramda working, noting that the 3rd Party Ramda model in deno.land does not work for me.

import { createRequire } from 'https://deno.land/std/node/module.ts'
const require = createRequire(import.meta.url)
export const R = require('ramda')

Abc

Similar to Express for Node.js, Abc is a Deno framework to create web application. I briefly tried Oak but was having problems with the RouterContext and json parsing in the POST request body

Overall, it is quite easy to work with, and the boilerplate code is kept to a minimum.

Deno.test

Writing end-to-end test is easy enough. I have the server running in one terminal using, and have the test running on another terminal. I use denon which is the deno replacement for nodemon, that automatically restart the deno project upon changes in source code.

Deno.test() is quite similar to other test framework, for example:

Deno.test('browse', async () => {
  await waitForServerToStart()
  const response = await fetch(getMediaApi())
  const result = await response.json()
  assertNotEquals(result.length, 0)
  const folder: MediaFolder = result[0]
  console.log(folder)
  assertStringContains(folder.url, 'stream')
  assertEquals(folder.name, 'stream')
  assert(folder.url.indexOf(' ') < 0, 'No space in url allowed')
})

The drawback of having server running on another terminal is that the tests could have started before the server is fully compiled and may not be up and running. So I inserted a little bit of code in the beginning of each test to retry until the the server is start.

const waitForServerToStart = async () => {
  let retryCount = 0
  while (retryCount++ < 10) {
    try {
      const response = await fetch(getMediaApi())
      console.log(`waitForServerToStart -> ${response.status}`)
      await response.json()
      if (response.ok) {
        return
      }
    }
    catch (ex) {
    }
  }
}