Can anyone explain the meaning of this code snippet:
myCollection: Collection|any = null;
I'm having trouble understanding it... Does it indicate that myCollection is set to type Collection, (which is an interface), with a default value of null? But what exactly does this part mean:
|any
Any insights would be appreciated!
| signifies a union. In the context of types, A | B means "either A, or B, or both".
any represents the concept of "any" type, which should be used sparingly as it disables type checking by being assignable to and from any other type. Consequently, any will override any type it is combined with in a union or intersection.
Hence, Collection | any translates to "either a Collection or any type at all". This ultimately simplifies to just any, since "either A or anything" equates to simply "anything":
myCollection: Collection | any = null;
// (property) Foo.myCollection: any
Therefore, the usage of Collection | any is primarily for documentation purposes; from the compiler's perspective, Collection | vanishes.
The property is initialized to null.
If this code does not belong to you, consider changing it to Collection | null if the intention is for the property to accept either a Collection or null. If it belongs to someone else, inquire about its purpose.
This signifies that myCollection can be assigned a value of type Collection or any, and is currently set to null.
When using Collection|any, the vertical bar symbol | represents a Union Type.
This means that the variable mycollection can contain a value of either type Collection or type any.
Since mycollection can be of type any, assigning null is considered a valid value and TypeScript allows you to do so.
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