类型校验保留字面量 satisfies

typescript📋 复制
type Config = {
  theme: 'light' | 'dark' | 'system'
  colors: Record<string, string>
}
// with a normal annotation you lose the literal type
const config1: Config = {
  theme: 'dark',
  colors: { primary: '#3d6fe8' }
}
// config1.theme is now 'light' | 'dark' | 'system', not 'dark'

// with satisfies, the shape is validated but types stay narrow
const config2 = {
  theme: 'dark',
  colors: { primary: '#3d6fe8', secondary: '#7c3aed' }
} satisfies Config// config2.theme is still 'dark' — the literal type is preserved
// config2.colors.primary is still 'string' — shape is validated
// if you typo a field name, TypeScript still catches it