KayodeIn cases where you want to construct a type with all properties of another type set to optional, the Partial<Type> is a helpful utility.
This is pretty useful when you need the subset of a given type.
For instance,
interface Person {
name: string;
age: number;
}
let persons: Person[] = [
{ name: "Abel", age: 19 },
{ name: "Drake", age: 23 },
{ name: "Lucid", age: 22 },
{ name: "Mark", age: 87 },
];
// takes an argument of
function searchBySub(subObj: Partial<Person>) {
return persons.find((person) => {
return Object.keys(subObj).every((key) => {
return person[key] === subObj[key];
});
});
}
The argument, subOj, can only be a sub-type of Person, so the code below would raise a type error
searchBySub({ unknownProperty: "unknown" })
// error - Argument of type '{ unknownProperty: string }' is not
// assignable to parameter of type 'Partial<Person>'
