TypeScriptDiscriminated union là union trong đó mỗi member có common literal property (discriminant).
TypeScript narrow type tự động khi check discriminant.
typescript
type Shape =
| { kind: 'circle'; radius: number }
| { kind: 'square'; side: number }
| { kind: 'triangle'; base: number; height: number };
function area(shape: Shape): number {
switch (shape.kind) {
case 'circle':
return Math.PI * shape.radius ** 2;
case 'square':
return shape.side ** 2;
case 'triangle':
return (shape.base * shape.height) / 2;
}
}Giúp type-safe handling cases khác nhau, TypeScript sẽ báo lỗi nếu thiếu case.
A discriminated union is a union where each member has a common literal property (the discriminant).
TypeScript automatically narrows the type when checking the discriminant.
typescript
type Shape =
| { kind: 'circle'; radius: number }
| { kind: 'square'; side: number }
| { kind: 'triangle'; base: number; height: number };
function area(shape: Shape): number {
switch (shape.kind) {
case 'circle':
return Math.PI * shape.radius ** 2;
case 'square':
return shape.side ** 2;
case 'triangle':
return (shape.base * shape.height) / 2;
}
}Provides type-safe handling of different cases — TypeScript reports an error if a case is missing.