sometimes you do that to avoid making your file a module.. we should check that the file is already a module before offering this suggestion, otherwise more errors would be produced.

just like you say "sometimes you do that to avoid making your file a module". @mhegazy
a.ts

import fs = require("fs");
namespace G {
    export let a = 0;
}

b.ts

G.a // error 

I want use namespace as global. not single module. but if use "import fs = require('fs')" in "a.ts", "b.ts" can't use G. if use "const fs = require("fs")", it's work.

"const fs = require("fs")" no intellisense in vscode, webstorm have intellisense. it's confuse me.

@WangPengJu require is just a function any => any -- webstorm must have a separate layer on top of TypeScript. I don't think there's any way to create a global namespace inside a module scope -- even in a commonjs system, a var in a module is still local, and that's what a namespace compiles to.

finally, i will merger all file in one file(as global). so that is why i use namespace. not module. @Andy-MS

const fs: typeof import ("fs") = require("fs");

it's work.
use typescript: 2.9.0-dev.20180501