In JavaScript, the value of the this operator is determined by the way a function or method is invoked. In a method, the this operator usually points to the class instance.
The polymorphic this type is an improved version of the original type inference for the this operator that introduced the following behavior as documented by Anders Hejlsberg:
- The type of this in an expression within a nonstatic class or interface member is an instance of some class that derives from the containing class, as opposed to simply an instance of the containing class.
- The this keyword can be used in a type position within a nonstatic class or interface member to reference the type of this.
- When a class or interface is referenced as ...
