Challenge Library
Coding Challenges
5,893 curated questions across every arena — browse by topic, then jump into a live 3-minute battle to put them to the test.
Filter by type
Filter by difficulty
Popular topics
1,575 challenges matching your filters
- Code AnalysisHard
Goroutine Capture
code-analysisGolanguage - Code AnalysisBeginner
Interface Conversion
code-analysisGolanguage - Code AnalysisHard
Iota Math
code-analysisGolanguage - Code AnalysisBeginner
Map Comma OK
code-analysisGolanguage - Code AnalysisHard
Named Return Shadow
code-analysisGolanguage - Code AnalysisHard
Nil Interface Trap
code-analysisGolanguage - Code AnalysisBeginner
Nil Slice Len
code-analysisGolanguage - Code AnalysisHard
Panic with Defer
code-analysisGolanguage - Code AnalysisHard
Range Pointer Trap
code-analysisGolanguage - Code AnalysisBeginner
Short Var Scope
code-analysisGolanguage - Code AnalysisHard
Slice Capacity Sharing
code-analysisGolanguage - Code AnalysisBeginner
String Immutability
code-analysisGolanguage - Code AnalysisIntermediate
Switch No Expression
code-analysisGolanguage - Code AnalysisHard
Type Assert Panic
code-analysisGolanguage - Code AnalysisHard
Trace: Default Sort
javascriptanalysishard - Code AnalysisIntermediate
Trace: Closure Counter
javascriptanalysisintermediate - Code AnalysisIntermediate
Trace: String Plus
javascriptanalysisintermediate - Code AnalysisHard
Trace: Reduce Without Init
javascriptanalysishard - Code AnalysisIntermediate
Trace: splice Return
javascriptanalysisintermediate - Code AnalysisBeginner
Trace: typeof null
javascriptanalysisbeginner - Code AnalysisBeginner
map transform
javascriptbeginner - Code AnalysisBeginner
filter even
javascriptbeginner - Code AnalysisBeginner
reduce sum
javascriptbeginner - Code AnalysisIntermediate
sort default
javascriptintermediate - Code AnalysisBeginner
sort numeric
javascriptbeginner - Code AnalysisIntermediate
splice modify
javascriptintermediate - Code AnalysisBeginner
slice copy
javascriptbeginner - Code AnalysisBeginner
spread merge (a08)
javascriptbeginner - Code AnalysisIntermediate
flat nested
javascriptintermediate - Code AnalysisBeginner
destructure rest
javascriptbeginner - Code AnalysisBeginner
find object
javascriptbeginner - Code AnalysisBeginner
some test
javascriptbeginner - Code AnalysisIntermediate
Closure basic
javascriptintermediate - Code AnalysisHard
Closure independence
javascripthard - Code AnalysisIntermediate
Private via closure
javascriptintermediate - Code AnalysisHard
Loop closure with let
javascripthard - Code AnalysisHard
Loop closure with var
javascripthard - Code AnalysisIntermediate
IIFE scope
javascriptintermediate - Code AnalysisBeginner
Block scope let
javascriptbeginner - Code AnalysisIntermediate
Closure updating
javascriptintermediate - Code AnalysisBeginner
DOM selection
javascriptbeginner - Code AnalysisIntermediate
classList add
javascriptintermediate - Code AnalysisIntermediate
setTimeout order
javascriptintermediate - Code AnalysisIntermediate
event currentTarget
javascriptintermediate - Code AnalysisIntermediate
event target
javascriptintermediate - Code AnalysisBeginner
innerHTML injection
javascriptbeginner - Code AnalysisIntermediate
appendChild return
javascriptintermediate - Code AnalysisBeginner
localStorage type
javascriptbeginner - Code AnalysisBeginner
removeChild
javascriptbeginner - Code AnalysisBeginner
try/catch
javascriptbeginner - Code AnalysisHard
finally with return
javascripthard - Code AnalysisBeginner
Error name
javascriptbeginner - Code AnalysisBeginner
instanceof Error
javascriptbeginner - Code AnalysisHard
Rethrow with cause
javascripthard - Code AnalysisIntermediate
JSON.parse error
javascriptintermediate - Code AnalysisBeginner
Promise rejection
javascriptbeginner - Code AnalysisBeginner
Destructuring default
javascriptbeginner - Code AnalysisBeginner
Spread array copy
javascriptbeginner - Code AnalysisBeginner
Map operations
javascriptbeginner - Code AnalysisBeginner
Set uniqueness
javascriptbeginner
Practice now, dominate the arena
Every challenge here is drawn from the live Code Royale pool. Review a question, then head to the arena to answer under pressure against a real opponent — 3-minute matches, Elo ranking, and badge tiers on the line.