ES6 re-exported values are wrapped into Getter

问题:

Can somebody explain this to me? Let's say I have these two modules:

// moduleTwo.js

export const module2Func = () => {
  return 2
}

And

// moduleOne.js

export * from './moduleTwo'

export const module1Func = () => {
  return 1
}

And then I import moduleOne somewhere:

import * as final from './moduleOne'

console.log(final) 

Then final results into something likes this:

{ module2Func: [Getter], module1Func: [Function: module1Func] }

Why is module2Func wrapped into a Getter? It is the export from that syntax does that? All functions work as expected. I'm using Babel 6 to transpiler code.

Thank you for any kind of explanation!

回答1:

That's Babel's doing to correctly implement reference binding of module imports. You can look at the compiled output.

Input:

export * from 'foo';

Output:

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _foo = require('foo');

Object.keys(_foo).forEach(function (key) {
  if (key === "default") return;
  Object.defineProperty(exports, key, {
    enumerable: true,
    get: function get() {
      return _foo[key];
    }
  });
});