Code Snippets

Here are some code snippets you might find useful. I leave them there when they don't deserve a library on their own.

You can find more on my Twitter account.

URL query string from object#


Create a URL with escaped query string arguments from an object, without any dependencies:

export function url(base: string, args: object): string {
  const url = new URL(base)
  Object.entries(args).forEach(([key, value]) => {
    url.searchParams.set(key, value)
  return url.toString()

// Example usage:
url('', {
  client_id: process.env.SPOTIFY_CLIENT_ID,
  redirect_uri: 'http://localhost:12345',
  response_type: 'token'
// ->

Browser support for URLSearchParams (used in url.searchParams):

Data on support for the urlsearchparams feature across the major browsers from

Interface type filtering#


Get the keys of an object for which the value is of a given type:

export type FilterKeys<Source, Condition> = {
  [key in keyof Source]: Source[key] extends Condition ? key : never
}[keyof Source]

// Example usage:
interface User {
  firstName: string
  lastName: string
  age: number

type UserStringKeys = FilterKeys<User, string> // 'firstName' | 'lastName'

Make RFCs easier to read#


Ahh RFCs, the core documentation of the Internet, so useful at times, but still visually anchored in the 1980s. Let's make them look nicer with a bit of CSS, shall we ?

Copy and paste this in your console when viewing an RFC:

    'margin:0 auto;font-size:16px;line-height:1.4;color:#333'