打字稿错误：app.ts（18,10）：错误TS2503：找不到命名空间'server'

Question

Here is very simple code:

"use strict";

import * as express from "express";

class Server {
    public app: express.Application;

    public static run(): Server {
        return new Server();
    }

    constructor() {
        this.app = express();
    }
}

var server = Server.run();
export = server.app;

When I try to compile it tsc app.ts I get an error:

app.ts(18,10): error TS2503: Cannot find namespace 'server'.

In spite of the error TSC creates output file (app.js)

Why do I get the error? What do I do wrong?

Answer 1

I changed your last line to export default server.app and it compiles fine.

You have a commonjs style export statement, not an ES6 export statement that typescript expects.

See the typescript specification for export syntax at https://www.typescriptlang.org/docs/handbook/modules.html

Typescript does support some export = syntax, however it is limited to class, interface, namespace, function, or enum.

The documentation states:

The export = syntax specifies a single object that is exported from the module. This can be a class, interface, namespace, function, or enum."