What are primitive data types in JavaScript?

Numbers, booleans, strings, bigint, undefined, null, symbols. Immutable, value-based, stack-stored basics.

JavaScript const vs let vs var—which to use?

Const for unchanging values, let for reassignment, var never. Block scope wins.

Reference. Changes propagate—watch for shared state bugs.

Staring at buggy JS code? Blame data types. Twenty years in, these fundamentals haven't changed, but they still wreck noobs and vets alike.

theAIcatchup Apr 10, 2026 4 min read

Primitives are immutable and value-based; non-primitives are mutable references. 𝕏
Use const and let over var for modern, scoped variables. 𝕏
JS's loose typing and JIT make it fast but buggy—TypeScript fixes incoming. 𝕏

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Originally reported by Dev.to