What this snippet does
When 'const' is used, the inferred type is a readonly tuple, causing errors if the function attempts to mutate the argument.
Expected output
Compile Error: Property 'push' does not exist on type 'readonly [1]'.
Why practise typing this
Typing inference deep dive 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 mutate an as const objectInference Deep Dive · advanced
- Using const modifier on a generic type parameterInference Deep Dive · advanced
- Preserving literal unions in a generic functionInference Deep Dive · advanced
- Declaring variables with primitive typesBasic Types · beginner