Uncapitalize<StringType>

INFO

The Uncapitalize<StringType> utility type is available starting from TypeScript version 4.1. For more information see in TypeScript Handbook, Release Note

Overview

The Uncapitalize<StringType> utility type in TypeScript is used to convert the first character of a string literal type to lowercase, while preserving the remaining characters unchanged. This is particularly useful for tranforming string literal types in a way that aligns with naming conventions or other requirements.

Syntax

type Uncapitalize<S extends string> = S extends `${inter F}${inter Rest}` ? `${Lowercase<F>}${Rest}` : S;

• StringType (S): The string that you want to convert the first character to an lowercase equivalent.

Examples

Example #1

type UppercaseGreeting = 'HELLO WORLD';
type UncomfortableGretting = Uncapitalize<UppercaseGreeting>; // 'hELLO WORLD'

type PascalCase = 'PascalCase';
type CamelCase = Uncapitalize<PascalCase>; // 'pascalCase'

Example #2

type ConfigOptions = 'MaxConnections' | 'TimeoutDuration' | 'RetryAttempts';

type ConfigKeys = Uncapitalize<ConfigOptions>;

const config: Record<ConfigKeys, number> = {
  maxConnections: 100,
  timeoutDuration: 5000,
  retryAttempts: 3,
};