出口进口<name>打字稿中的语法？</name>

Question

While browsing a declaration file on dt I came accross the following syntax:

import github = Strategy; // <- what is imported from where here?

declare class Strategy extends oauth2.Strategy {
     ...
}

declare namespace Strategy {
    export import Strategy = github; // <- I've not seen this syntax before?

    interface _StrategyOptionsBase {
      ...
    }
}

export = Strategy;

I'm having trouble understanding the import and export syntax here. I roughly understand typescripts export= custom syntax . However, I don't understand why and what we're exporting from the namespace. Nor do I fully understand what we're importing with import github... .

I'd love some help.

Answer 1

import github = Strategy;

this syntax describes a namespace alias.

Another way that you can simplify working with namespaces is to use import q = xyz to create shorter names for commonly-used objects.

 namespace Shapes { export namespace Polygons { export class Triangle {} export class Square {} } } import polygons = Shapes.Polygons; let sq = new polygons.Square(); // Same as 'new Shapes.Polygons.Square()'

source

---

export import Strategy = github

is a combination of renaming the namespace and exporting it again with the new name. You can't write something like

declare namespace Strategy {
    export namespace Strategy;
}

so this looks like a workaround to achieve what is done in the passport-github source code.

// Load modules.
var Strategy = require('./strategy');

// Expose Strategy.
exports = module.exports = Strategy;

// Exports.
exports.Strategy = Strategy;

source

exports = module.exports = Strategy;

this line exports Strategy as default export, the counterpart in the typescript definition is

export = Strategy

Then passport-gitlab also export Strategy as property on the default export.

exports.Strategy = Strategy;

You can think of it like a class that has a static property which references the class.

class Strategy {
    static Strategy: typeof Strategy
}
export = Strategy