What this snippet does
With strictNullChecks, you must explicitly check that optional or nullable variables are defined before accessing their properties.
Expected output
Unknown
Why practise typing this
Typing tsconfig & compiler code builds muscle memory for the symbols and indentation TypeScript uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
More TypeScript practice
- Enabling strict mode in tsconfigtsconfig & Compiler · intermediate
- Strict null checks preventing undefined accesstsconfig & Compiler · intermediate
- Implicit any in function parameters under stricttsconfig & Compiler · intermediate
- Preventing null assignment to stringstsconfig & Compiler · intermediate
- Array index access returns T instead of T | undefinedtsconfig & Compiler · intermediate
- Catching implicit any in variablestsconfig & Compiler · intermediate