rpivo

Using Custom CLI Parameters in Node

In the following TypeScript example, we're expecting two possible CLI parameters, --build and --port. We prepare a paramMap variable that has default values for all parameters, which are overwritten for each parameter that is manually passed in via the CLI.

See further down for a TypeScript example without comments as well as a JavaScript example.

// create an enum that contains each of the params
enum Params {
  BUILD = '--build',

rpivo

JSON & Serialization

Looking at the JSON documentation, JSON doesn't support a lot of JavaScript values for the reason that there's no way to translate these values to other languages, and therefore the values are not serializable.

Not being serializable means that a value can't be converted into a string and then later parsed from the string with 100% certainty of what the value should represent in the new context with which the value is being parsed.

For example, if a JavaScript function should be serialized within a JSON string, and if this JSON string is passed into a Python context, Python won't have any idea what to do with this function since it uses JavaScript language features and syntax that aren't available in Python.

Below is an object that we're stringifying and then parsing with JSON. We can get a sense of what is and isn't serializable in JavaScript this way.

rpivo

BigInt in JavaScript

BigInt is a relatively new JavaScript data type introduced in 2020.

JavaScript's original Number primitive can only represent numbers up to 2⁵³ - 1.

We can log this maximum value with Number.MAX_SAFE_INTEGER:

console.log(Number.MAX_SAFE_INTEGER)
// 9007199254740991

rpivo

Working With Promises

• Promise States
• Promise Methods
• Creating a Promise
• The Promise Callback Signature
• Exploring Asynchrony in Promises
• Comparing Promises & SetTimeouts
• Then, Catch, & Finally Branches
• Piping Data Through Branches
• Throwing an Error in a Branch

rpivo

Point-Free Style in JavaScript

Point-free style is a really cool mechanic that can help establish good practices in regards to functional programming.

const arr = [1,2,3]

arr.forEach(console.log)

rpivo

Killing a Process on a Specific Port on Windows

This gist is based on this Stack Overflow answer.

For the below commands, imagine we're running a process on port 3000, and we want to kill it.

To kill a process on a specific port on Windows, first run:

netstat -ano | findstr :3000

rpivo

Installing Pip on Mac From the Terminal

For more ways to install, go to the official documentation.

Check if pip is already installed:

python -m pip --version

rpivo

Checking if a Substring Exists in a String in Python

allowed = 'abc'
word = 'cat'
for char in word:
  if char in allowed: print(char) # prints 'c', 'a',
  if char not in allowed: print(char) # prints 't'

rpivo

Using Map in Python

Python's map function works similarly to JavaScript's map. To use it, you must supply as a first argument a callback or lambda function that will perform work on each item in a given iterable. For its second argument, you pass in the iterable itself.

def increment(n: int) -> int:
  return n + 1

l = [1,2,3]

rpivo

Python String Constants

You can import string constants from string.

• ascii_lowercase ‘abcdefghijklmnopqrstuvwxyz’
• ascii_uppercase ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’
• ascii_letters ‘ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz’
• digits ‘0123456789’
• hexdigits ‘0123456789abcdefABCDEF’
• octdigits ‘01234567’