Mark

Everything software engineering

[Mark @software_mark_]

365 days. 1 book series. Daily JS lessons.
I’m committing to reading “You Don’t Know JS Yet” by Kyle Simpson , all 6 books , every day for a year and tweeting everything I learn.
If you’re on the same journey, follow along, let’s do this together. 🤝.
#365DaysOfYDKJS #YDKJS.

[Beni💗 @0x_beni_]

I didn’t win the Google Gemma Hackathon but the number of opportunities I have gotten from this project has been overwhelming

Grateful to God💗

[Mark @software_mark_]

Scopes are determined at compile time in JavaScript.

Not at runtime. Not when the function runs. At compile time.

That one sentence changes how you read and write JS forever. 🧩

#365DaysOfYDKJS #YDKJS #JavaScript #LearnInPublic

[Mark @software_mark_]

Every variable in JavaScript does one of two things:

🔹 Receives a value → Target (LHS)
🔹 Provides a value → Source (RHS)
Understanding this is the foundation of how scope resolution works in JS. 💡

#JavaScript #YDKJS #365DaysOfYDKJS

[Mark @software_mark_]

The Temporal Dead Zone is one of the most misunderstood concepts in JS.

let and const are hoisted — but not initialized.

Access them before initialization and JS throws an error. Not undefined. An actual error. 👀

console.log(x) // ❌ TDZ Error
let x = "hello"

#JavaScript #YDKJS #365DaysOfYDKJS

[Mark @software_mark_]

Most people think JavaScript executes line by line.

But if it did — a syntax error on line 10 wouldn't stop line 1 from running.

It does. And that proves JS is compiled before execution. 🧠

#JavaScript #YDKJS #365DaysOfYDKJS

[Mark @software_mark_]

That's Day 14 done. 🎯

Three proofs. One conclusion — JavaScript is compiled before it executes.

See you for Day 15. 👇

#365DaysOfYDKJS #YDKJS #JavaScript #LearnInPublic

[Mark @software_mark_]

Day 14 of 365 — #365DaysOfYDKJS 🧵

Yesterday I said there are 3 things that prove JavaScript is compiled before execution.

Today we go through all three. Let's get into it 👇

#YDKJS #JavaScript #LearnInPublic

[Mark @software_mark_]

6/ Variables in JS do one of two things:

🔹 Target (LHS) → receiving an assignment
var greeting = "Hello" // greeting is a target
🔹 Source (RHS) → providing a value
console.log(greeting) // greeting is a source

[Mark @software_mark_]

That's Day 13 done. 🎯

Book 2 is already going deep — and we're just getting started.

See you tomorrow for Day 14. 👇

#365DaysOfYDKJS #YDKJS #JavaScript #LearnInPublic

[Mark @software_mark_]

Day 13 of 365 — #365DaysOfYDKJS 🧵

Starting Book 2 — Scopes & Closures today.

First up — revisiting why JavaScript is more compiled than most people think. Let's get into it 👇

#YDKJS #JavaScript #LearnInPublic

[Mark @software_mark_]

5/ Three things prove that JS is parsed and compiled before execution:

1️⃣ Syntax Errors
2️⃣ Early Errors
3️⃣ Hoisting
More on each of these tomorrow. 👀
#YDKJS #365DaysOfYDKJS #JavaScript