I have this piece of code (from here), that I am trying to understand what it does:

declare global {
  interface Window { analytics: any; }
}

I have seen here what declare global means.

And I have seen from this question what interface means.

I know what the window object means.

What I do not understand is what the code above means. Correct if I am wrong. The code means that the analytics variable has is now recognized as a global object of type any. Also that it has the window properties that you can access, as shown by interface Window.

Also why do we declare global{ /**variable being declared gloabal here.*/ }. Why are we using this semantic to declare a global variable. Why does the variable go inside the curly braces as opposed to something like var goat?

CodePudding user response：

This is called Global augmentation, it's a special syntax/keyword which allows to declare global variables. These declarations get merged with the ECMAScript definition files thanks to the declaration merging ability of TypeScript.