typescript 类型声明在 IDE 中显示错误

Question

I have the following type definition:

export type AuthType = boolean | { roles: string[]; assistant?: string[] } | (() => void);

Now I have a line of code in which I want to check the type of my auth variable and assign a value or execute a function:

req.allowed = auth === true ? this.allowed : auth.roles ? auth : auth();

The code works fine (this line is only executed if auth is not false or null) but my IDE (webstorm) shows me the following error:

Answer 1

You haven't checked whether or not auth is an object, so typescript is trying to prevent you from accessing the roles property on a function (which doesn't exist). Note that this won't throw an error but might be confusing to a future reader of the code.

The way you have it set up, you probably want to use the optional chaining operator :

req.allowed = auth === true ? this.allowed : auth?.roles ? auth : auth();

This will make it so that auth?.roles evaluates to undefined if it is a function.