What this snippet does
The 'infer extends' syntax constrains the inferred type, ensuring it matches a specific shape before assigning it.
Expected output
a
Why practise typing this
Typing type manipulation 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
- Creating a type from string literalsType Manipulation · advanced
- Generating event listener names from propertiesType Manipulation · advanced
- Assigning a raw string to a template literal typeType Manipulation · advanced
- Uppercasing a string literal typeType Manipulation · advanced
- Creating a constant case from camelCaseType Manipulation · advanced
- String manipulation utils only work on literal typesType Manipulation · advanced