Capitalize and Uncapitalize types in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Capitalize type do in TypeScript?

The Capitalize type changes the first character of a string type to uppercase, leaving the rest unchanged.

beginner

What is the purpose of the Uncapitalize type in TypeScript?

The Uncapitalize type changes the first character of a string type to lowercase, leaving the rest unchanged.

beginner

How would you capitalize the string literal type "hello" using TypeScript's utility types?

You can use Capitalize<"hello"> which results in the type "Hello".

beginner

Given the type type Lower = Uncapitalize<"World">;, what is the resulting type?

The resulting type is "world", where the first letter is converted to lowercase.

intermediate

Can Capitalize and Uncapitalize be used with general string types (like string)?

No, they only work with string literal types or unions of string literals, not with the general string type.

What does Capitalize<"typescript"> evaluate to?

A "Typescript"

B "typescript"

C "TYPESCRIPT"

D "tYpescript"

Capitalize changes only the first letter to uppercase, so "typescript" becomes "Typescript".

What is the result of Uncapitalize<"Hello">?

A "Hello"

B "hello"

C "HELLO"

D "hELLO"

Uncapitalize converts the first letter to lowercase, so "Hello" becomes "hello".

Which of these types can Capitalize be applied to?

A General <code>string</code> type

B Number types

C String literal types

D Boolean types

Capitalize works only on string literal types, not on general string or other types.

What happens if you apply Capitalize to an empty string literal ""?

A It returns <code>"undefined"</code>

B It throws a compile error

C It returns <code>" "</code> (space)

D It returns <code>""</code> (empty string)

Applying Capitalize to an empty string returns the empty string unchanged.

Which utility type would you use to make the first letter of a string lowercase?

A Uncapitalize

B Capitalize

C Uppercase

D Lowercase

Uncapitalize converts the first letter of a string literal to lowercase.

Explain how the Capitalize and Uncapitalize types work in TypeScript and give an example of each.

Think about how these types transform the first character of a string.

Describe a situation where using Capitalize or Uncapitalize types would be helpful in a TypeScript project.

Consider when you want to enforce or transform string formats in types.