In TypeScript, the question mark ? is used to indicate an optional property or parameter.
For example if an interface (with the name ‘User’) has been defined that has the email property which is marked with a question mark. It indicates that it is optional. This means that a User object can be created with or without an email property.
Similarly, the question mark can be used to indicate an optional parameter in a function.
If a function with two parameters is using age parameter with a question mark, it indicates that it is optional. This means that the function can be called with one or two arguments, and will behave differently depending on whether the age argument is provided.
Overall, the question mark in TypeScript is used to indicate optional properties or parameters, which can help make your code more flexible and easier to use in a variety of contexts.