TypeScript Compilation Error - Type Mismatch
TypeScript reports type errors that prevent build. Type checking fails even though code appears correct.
Build exits with 'TypeScript error found' message.
Error Messages You Might See
Common Causes
- Variable assigned wrong type
- Function argument type mismatch
- Null/undefined not handled properly
- Object or array structure mismatch
- Missing type definitions for library
How to Fix It
Read error message carefully - shows exact line and issue
Use 'as' type assertion sparingly: value as string only when you're sure
Fix null/undefined: use optional chaining (obj?.prop) and nullish coalescing (val ?? default)
For library missing types: npm install @types/library-name
Temporary: add // @ts-ignore above problematic line, then fix later
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Get HelpFrequently Asked Questions
What's the difference between unknown and any?
unknown is safe - requires type checking. any bypasses checking entirely. Always prefer unknown
How do I handle null/undefined?
Use optional chaining: obj?.prop?. Use nullish coalescing: val ?? default
Should I use 'as' type assertion?
Rarely. It bypasses type checking. Use when you're 100% sure of the type