What this snippet does
Using readonly prevents accidental mutation of sensitive object properties during runtime.
Expected output
123-45
Why practise typing this
Typing objects and interfaces 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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- Attempting to reassign a readonly propertyObjects and Interfaces · beginner
- Passing an exact object literal to an interfaceObjects and Interfaces · beginner