| name | roblox-luau-core |
| description | Use for Luau syntax, tables, control flow, string patterns, math, scope, closures, idioms, or porting code from JavaScript or Python. |
| last_reviewed | "2026-05-27T00:00:00.000Z" |
| sources | ["https://luau-lang.org/","https://create.roblox.com/docs/luau"] |
Luau Core Language
When to Load
Load for Luau syntax questions: variables, operators, tables, string patterns, math helpers, scope/closures, common idioms, porting from JS/Python, and sharp edges (1-based indexing, nil semantics, truthiness). For type annotations, use roblox-luau-types. For OOP/async/modules, use roblox-luau-patterns.
Hand off to: roblox-luau-types (type annotations/generics), roblox-luau-patterns (OOP/async/modules), roblox-* domain skills (engine APIs).
Full reference: references/full.md
Quick Reference
Basics: Luau = Lua 5.1 + extensions. Always local. No hoisting — callees above callers. Forward-declare for mutual recursion.
Extensions over Lua 5.1: continue, += -= *=, // floor division, math.clamp/sign/round, backtick interpolation, generalized iteration, table.freeze/clone/clear.
Truthiness: Only nil and false are falsy. 0, "", {} are truthy. No type coercion in == (0 == "0" → false).
Arrays: 1-based. #tbl length — unreliable with nil gaps, keep contiguous. Use table.insert/remove/find/sort/concat. Iterate: for k, v in tbl do.
Strings: Prefer backticks `{name} age {age}` over ... Patterns (NOT regex): %a %d %w %s classes, * + - ? quantifiers, ^$ anchors. Functions: string.match/gmatch/gsub/split.
Tables: Only compound type. Reference semantics (= aliases). table.clone is shallow. nil removes keys. Dynamic keys need bracket notation t[key].
Ternary: (cond and val or fallback) breaks if val is falsy. Use if cond then a else b for safety.
Error handling: pcall(fn) / xpcall(fn, handler). No try/catch.
Pitfalls:
a and b or c fails when b is nil/false- Arrays start at 1, not 0
: defines implicit self, . doesn't- While-loop closures share variable — capture in local
- No arrow functions,
===, !=, spread, const/let
- Reserved keywords can't be identifiers (
return, continue, etc.)
- Use
task.wait/spawn/delay, never deprecated wait/spawn/delay
JS→Luau: map/filter → manual loops, null → nil, x ?? y → x or y, x?.y → x and x.y, === → ==, !== → ~=, import → require, class → metatable+__index, try/catch → pcall.
For detailed examples, see references/full.md.
