typescript / expert
Snippet
Precise Validation with the 'satisfies' Operator
The 'satisfies' operator validates that an object matches a type without widening its inferred type. This allows you to keep specific literal information (like knowing 'red' is a tuple) while ensuring the object conforms to a general interface.
snippet.ts
typescript
1
2
3
4
5
6
7
8
9
10
11
type Colors = "red" | "green" | "blue";type RGB = [number, number, number];const palette = {red: [255, 0, 0],green: "#00ff00",blue: [0, 0, 255]} satisfies Record<Colors, RGB | string>;// palette.red is inferred as [number, number, number], not string | RGBconst redValue = palette.red[0];
Breakdown
1
satisfies Record<Colors, RGB | string>
Checks compatibility with the Record type without overwriting the specific inferred shapes of the properties.
2
palette.red[0]
Safe access is possible because 'satisfies' preserved the knowledge that 'red' is exactly an RGB tuple.