What this snippet does
Custom guards encapsulate complex runtime validation logic into reusable type-safe functions.
Expected output
true
Why practise typing this
Typing type guards 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
- Narrowing a union with typeofType Guards · beginner
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- Narrowing class instances with instanceofType Guards · beginner
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- Using instanceof on primitive stringsType Guards · beginner