Interactive Cheatsheets
Master JSON parsing, validation, and design patterns.
Circular Reference
Errors when an object references itself directly or indirectly.
Complex Objects Breakdown
Functions, Symbols, and undefined are lost.
Null vs Missing Field
Ambiguity between "unknown value" and "no value".
Inconsistent Field Types
A field that changes type (e.g., string then object).
Arrays with Mixed Shapes
Arrays containing objects with different schemas.
Type Loss (Date, Map, Set)
Special JS objects turn into generic structures.
Large Number Precision
64-bit float limits modify large integers.
Booleans as Strings
"false" is truthy in Boolean("false").
ID Types: Number or String?
Mixing 123 and "123" creates matching issues.
Non-Standard Date Formats
Using local formats like "12/01/2023".
Undefined Removed Silently
Key-value pairs disappear if value is undefined.
Dynamic/Random Keys
Using IDs as keys makes iteration hard.
Shape-Shifting Objects
Objects changing schema based on context.
Over-Nesting
Deeply nested structures are hard to read and parse.
Key Order Uncertainty
JSON object keys are technically unordered.
Error Object Serialization
Standard JS Errors serialize to empty objects `{}`.
Giant Payloads
Sending MBs of data without pagination.
Overloaded Fields
A field doing too many things.
No API Versioning
Breaking changes break clients immediately.
Semantically Incorrect
Valid syntax but nonsensical data.