What this snippet does
Constraints (extends) restrict generics to types matching a specific shape, unlocking access to that shape's properties.
Expected output
4
Why practise typing this
Typing generics 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
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- Using an interface without providing type argumentsGenerics · intermediate