ES6：按需导入指定值至命名空间，如何避免变量重复？

Great question! I totally get why you’d want to avoid cluttering your module scope with extra variables when you only need them grouped in a namespace object. Let’s break down a few clean, straightforward solutions to fix this:

1. Import the entire module, then cherry-pick properties #

This is the simplest static import approach. By importing the full module as a single object, you can pull just the values you need into your constants object without leaving a and c floating around in the module scope:

// module2.js
import * as module1 from './module1.js';

const constants = {
  a: module1.a,
  c: module1.c
};

Now only module1 (the full imported module) and constants exist in your top-level scope—no stray a or c variables to worry about.

2. Use an IIFE with dynamic import (for async contexts) #

If you’re working in an environment that supports top-level await (like modern browsers or Node.js), you can wrap a dynamic import in an IIFE to keep a and c confined to a local scope:

// module2.js
const constants = await (async () => {
  const { a, c } = await import('./module1.js');
  return { a, c };
})();

Here, a and c only exist inside the IIFE’s scope, so they never leak into your module’s top-level scope.

3. Use Object.fromEntries for scalable selections #

If you need to pick multiple properties (and might add more later), Object.fromEntries makes this cleaner and easier to maintain. Just define the keys you want, then map them to the imported module’s values:

// module2.js
import * as module1 from './module1.js';

const keysToInclude = ['a', 'c'];
const constants = Object.fromEntries(
  keysToInclude.map(key => [key, module1[key]])
);

This way, updating which properties you include is as simple as modifying the keysToInclude array—no need to rewrite the entire object literal.

All these methods ensure a and c live only within your constants object (or the imported module object, which is intentional) while keeping your module scope clean. The first approach is the most widely compatible and works in all static import scenarios, while the others offer flexibility for specific use cases.

内容的提问来源于stack exchange，提问作者maillard