Declare Typescript global variable as “module” type

Question

I have the React type definition file (that is declared using an external module). In my source files, I usually do:

import * as R from \"react\"


        

Answer 1

The declare keyword does not declare a variable in the global scope. This keyword is used for cases in which there will be a variable in the global scope and you want to use it in a TypeScript without getting compilation errors.

You can declare a global variable with:

import * as R from "react";
window.R = R;

Answer 2

instead have it as a global

There are two sides to this: global type declaration for typescript and global variable availability for JavaScript consumption.

Global Type Declaration

A .d.ts or a declaration only contributes to the global name declaration space if there is no root level import or export in the file. So have a file globalreact.d.ts which will be an edited version of https://github.com/borisyankov/DefinitelyTyped/blob/master/react/react.d.ts of the form declare module R (instead of declare module "react").

Global Variable Export

You need to put it on window in case of the browser. So do the following in a file makeReactGlobal.ts:

var R = require('react'); 
(<any>window).R = R

And then in your application main have this file a dependency to ensure that it executes before any of your other code.

Answer 3

Like @basarat said, it doesn't look like it's possible. @ahejlsberg himself weighed in on the issue on github: https://github.com/Microsoft/TypeScript/issues/3180#issuecomment-102523512.