Roblox luau core

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.