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The satisfies Operator for Config Objects

Use satisfies to check a config literal against a broad type while preserving its literal inference, catching typos without widening values.

TypescriptConfig Management

Code

snippet
type Theme = "light" | "dark" | "system";

interface AppConfig {
  theme: Theme;
  locale: string;
  features: Record<string, boolean>;
}

export const config = {
  theme: "dark",
  locale: "en-US",
  features: { search: true, beta: false },
} satisfies AppConfig;

// config.theme is inferred as "dark", not widened to Theme:
export type ThemeValue = typeof config.theme;

export function resolveTheme(value: ThemeValue, prefersDark: boolean): "light" | "dark" {
  if (value === "system") return prefersDark ? "dark" : "light";
  return value;
}

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