Try the first 5 questions here — click a question, type your prediction, see if you got it right. The rest are in the interactive quiz. These questions are designed to expose blind spots — you need to predict, not read.
🎯 Why interviewers love these questions
They test your mental model of JavaScript's type system — the Abstract Equality Comparison algorithm, how coercion fires, how the event loop orders execution. A developer who can't explain [] == false probably also writes coercion bugs in production.
Misc Quirks
#16
Comma Operator Evaluation
HardMisc Quirks
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Type Coercion
#01
NaN comparison is always false
EasyType Coercion
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#02
Loose equality treats 0 and "" as false
EasyType Coercion
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#03
Plus operator concatenates strings instead of adding
MediumType Coercion
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#04
Plus operator: string concat vs numeric add
EasyType Coercion
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#05
Loose equality edge cases with null
MediumType Coercion
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#06
typeof for common values
EasyType Coercion
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#07
Unary plus converts to number
MediumType Coercion
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#08
null comparison inconsistency
HardType Coercion
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#09
Object valueOf for arithmetic, toString for template
HardType Coercion
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#10
parseInt stops at first invalid character
MediumType Coercion
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#11
String comparison is lexicographic
MediumType Coercion
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#12
Array coercion with plus operator
HardType Coercion
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#13
NaN is not equal to anything including itself
EasyType Coercion
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#14
Object equality is reference-based
MediumType Coercion
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#15
String spread — unicode-safe character split
MediumType Coercion
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Type Conversion
#17
Implicit Numeric Conversion
HardType Conversion
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12 more tricky questions in the quiz
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