I'm learning Angular and reading through the documentation but I'm confused why the bitwise OR operator is being used in the product variable declaration below. What does the product: Product | undefined line mean?
export class ProductDetailsComponent implements OnInit {
product: Product | undefined;
/* ... */
}
In that context it is not the OR operator but a "Union Type".
In TypeScript, a union type variable is a variable which can store multiple type of values (i.e. number, string etc).
A union type allows us to define a variable with multiple types. The union type variables are defined using the pipe ('|') symbol between the types.
Source: https://howtodoinjava.com/typescript/union-types/
So this means that product must be of type Product or undefined. (the undefined part is only relevant if you have strictNullChecks enabled).
Another way to write this is
product?: Product;
Where the question mark indicates that it is an optional parameter.