What this snippet does
Assertions compile successfully but cause runtime errors if the actual type doesn't match the asserted type.
Expected output
TypeError: str.toUpperCase is not a function
Why practise typing this
Typing variables and declarations 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.
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