I believed React is smart enough to know this…. but aye?

We had a bunch of large component trees in our company’s web application. And I saw them re-rendering from the top to deep down to the bottom for no reason. At first, I thought it would be easy to get them correct.

Of course, the tree was much bigger than…


Docker + TS + Terraform + Lambda + ECR + SAM CLI = 💚

This is a full guide to setup, develop and deploy a backend app with a recently released container image feature for lambda on AWS.

Needless to say, if you are a great fan of Docker, you would know how amazing it is. …


Disclaimer: We will focus on useSelector itself in this article, rather than third-party libraries like reselect, because it's out of the scope of the article.

How was it like before?

Now, before talking about useSelector, we need to know some background. Let's go back to pre-function component era, where all we needed to care about…


Yes, Chrome’s performance tab is overwhelming

First time you look into all the charts, you have no idea what means what. What do those different colors even mean? It’s not self-explanatory at all. There needs to be a guidebook.

In this article,

  1. I will briefly walk you through all functionalities of Chrome’s performance tab, with majority…


Just a random image like everyone else does (credit: Genessa Panainte from unsplash)

I was struggling at my company trying to write some tests for redux-observable operations. Most of the network requests were managed by RxJS, and none of them were covered by tests. I wanted to write tests but just did not know how to.

But I really just wanted to start…


Oddities with how forEach works in JavaScript

Walking dead!!

I was coding as usual. And I faced an odd encounter with how forEach works. Here goes the code to give an example of that. Imagine the code below is the code from one of the libraries I was using:

And I spotted the code in my company’s app…

Joel Mun

Code/Security stuffs, mostly related to React, Typescript, and Node, GoLang, Wasm. https://9oelm.github.io.

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