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) => { // error: `this` implicitly has type `any`
A workaround is to replace this with the object:
foo.on('error', (err: any) => {
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:
This question is related to
typescript
typescript2.0
The answer is
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) => { // 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.
For method decorator declaration
with configuration "noImplicitAny": true,
you can specify type of this variable explicitly depends on @tony19's answer
function logParameter(this:any, target: Object, propertyName: string) {
//...
}
Source: Stackoverflow.com