0const user = { name: "Alice", age: 30 } satisfies { name: string; age: number };
| Step | Action | Evaluation | Result |
|---|---|---|---|
| 1 | Declare object 'user' with name and age | user = { name: "Alice", age: 30 } | Object created with exact types: name as "Alice", age as 30 |
| 2 | Apply 'satisfies' operator with type { name: string; age: number } | Check if user matches type shape | True: user matches the type shape |
| 3 | Keep 'user' exact types without widening | user.name is "Alice" (literal), user.age is 30 (literal) | Exact types preserved, not widened to string or number |
| 4 | Use 'user' safely with type guarantees | Access user.name and user.age | No type errors, properties exist as expected |
| 5 | End of execution | No errors or warnings | Execution successful |
| Variable | Start | After Step 1 | After Step 2 | After Step 3 | Final |
|---|---|---|---|---|---|
| user | undefined | { name: "Alice", age: 30 } (exact types) | Matches type { name: string; age: number } | Exact types preserved (name: "Alice", age: 30) | Final object with exact types and type safety |
Satisfies operator syntax:
const obj = { ... } satisfies Type;
It checks if obj matches Type shape
without widening literal types.
Use it to keep exact types
and ensure type safety.What does the satisfies operator do in TypeScript?
satisfiessatisfies operator checks if a value fits a type but keeps the original value unchanged.satisfies only verifies compatibility without altering the value.satisfies = type check only [OK]Which of the following is the correct syntax to use the satisfies operator in TypeScript?
const data = { name: "Alice", age: 30 } ___ Person;satisfiessatisfies operator is used between the value and the type like: value satisfies Type.satisfies to check the type without changing data.satisfies keyword [OK]What will be the output of this TypeScript code?
type Person = { name: string; age: number };
const user = {
name: "Bob",
age: 25,
city: "Paris"
} satisfies Person;
console.log(user.city);satisfies does to the objectsatisfies operator checks that user matches Person type but keeps all original properties, including city.user still has city, logging user.city prints "Paris" without error.satisfies keeps extra properties [OK]Identify the error in this TypeScript code using satisfies:
type Config = { port: number; host: string };
const serverConfig = {
port: "8080",
host: "localhost"
} satisfies Config;serverConfigport property is a string "8080" but Config expects a number.satisfies checkssatisfies verifies type compatibility and will raise a type error because of the wrong type for port.You want to create a constant object settings that must have theme as a string and notifications as a boolean. You also want to keep extra properties without losing their types. Which code correctly uses satisfies to achieve this?
settings to be checked against a type but keep extra properties like version with their types intact.satisfies which checks the required properties but keeps extra ones with full types. const settings: { theme: string; notifications: boolean } = { theme: "dark", notifications: true, version: 2 }; uses type annotation which drops extra properties. const settings = { theme: "dark", notifications: true, version: 2 } as { theme: string; notifications: boolean }; uses type assertion which forces the type and may lose extra property types. const settings = { theme: "dark", notifications: true, version: 2 }; has no type checking.satisfies keeps extra properties typed [OK]Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.