Explain template literal types and their use cases.

Template literal types create string patterns at the type level for powerful string manipulation. Basic Template Literals: type World = 'world'; type Greeting = \`hello ${World}\`; // 'hello world' type EmailLocaleIDs = 'welcome_email' | 'email_heading'; type FooterLocaleIDs = 'footer_title' | 'footer_sendoff'; type AllLocaleIDs = \`${EmailLocaleIDs | FooterLocaleIDs}_id\`; // 'welcome_email_id' | 'email_heading_id' | 'footer_title_id' | 'footer_sendoff_id' API Route Generation: type HTTPMethod = 'GET' | 'POST' | 'PUT' | 'DELETE'; type Resource = 'users' | 'posts' | 'comments'; type APIRoute = \`/${Resource}\` | \`/${Resource}/${string}\`; type RouteHandler = { [K in HTTPMethod as \`${K} ${T}\`]: (req: Request) => Response; }; // Usage const handlers: Partial> = { 'GET /users': (req) => { /* ... */ }, 'POST /users': (req) => { /* ... */ } }; CSS-in-JS Type Safety: type CSSProperties = { color?: string; backgroundColor?: string; fontSize?: string; }; type StyledComponent = { [K in T as \`${K}Styled\`]: (props: CSSProperties) => JSX.Element; }; // Generate styled components type ButtonComponents = StyledComponent<'primary' | 'secondary'>; // { primaryStyled: ..., secondaryStyled: ... } Benefits: • Type-safe string manipulation at compile time • Generate API routes and handlers • Create CSS-in-JS type safety • Build complex string patterns • Enable advanced metaprogramming.