Typescript: why am i getting a 'property does not exist on type' error?

Example:

interface Person {
    name: string;
}
const person: Person = {
    name: 'John',
    age: 25  // Error: Property 'age' does not exist on type 'Person'.
};

Solution:

interface Person {
    name: string;
    age: number;  // Added 'age' property to the interface
}
const person: Person = {
    name: 'John',
    age: 25
};

Ensure that all properties of your object match the properties declared in the corresponding type or interface.