Accept only valid property names for a given object type.
Section: Generics
Constrain a key parameter with `keyof`
typescript
typescript
function getProp<T, K extends keyof T>(obj: T, key: K): T[K] {
return obj[key];
}Explanation
This is one of the most useful generic patterns in application code.
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Same sheet · prioritizing Generics
Generic identity function
Use a type parameter for reusable function typing.
Generic array helper
Write array helpers that preserve element types.
Constrain generic types
Require a minimum shape for a type parameter.
Use indexed access types
Get a nested property type from another type.