this implicitly has type any because it does not have a type annotation

Question

When I enable noImplicitThis in tsconfig json  I get this error for the following code     this  implicitly has type  any  because it does not have a type annotation     class Foo implements EventEmitter     on name  string  fn  Function        emit name  string         const foo   new Foo    foo on  error   function err  any      console log err     this emit  end        error   this  implicitly has type  any        Adding a typed this to the callback parameters results in the same error   foo on  error    this  Foo  err  any    gt       error   this  implicitly has type  any    A workaround is to replace this with the object   foo on  error    err  any    gt      console log err     foo emit  end          But what is the proper fix for this error     UPDATE  It turns out adding a typed this to the callback indeed addresses the error  I was seeing the error because I was using an arrow function with a type annotation for this

User · Accepted Answer

The error is indeed fixed by inserting this with a type annotation as the first callback parameter  My attempt to do that was botched by simultaneously changing the callback into an arrow-function   foo on  error    this  Foo  err  any    gt       DON T DO THIS   It should ve been this   foo on  error   function this  Foo  err  any      or this   foo on  error   function this  typeof foo  err  any        A GitHub issue was created to improve the compiler s error message and highlight the actual grammar error with this and arrow-functions

User · Answer

For method decorator declaration with configuration  quot noImplicitAny quot   true  you can specify type of this variable explicitly depends on  tony19 s answer function logParameter this any  target  Object  propertyName  string

[typescript] 'this' implicitly has type 'any' because it does not have a type annotation

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