如何将带调用的require语句转换为ES6的import语法？

Great question! Let's unpack what's going on here and how to convert this CommonJS syntax to proper ES6 modules.

Why the original syntax works #

The line const uu = require('url-unshort')() tells us the url-unshort module exports a factory function—not the ready-to-use utility object directly. When you run require('url-unshort'), you retrieve that factory function, and the trailing () immediately calls it to initialize and return the actual uu object you'll use for expanding short URLs.

ES6 Module Conversion Options #

Since ES6 modules handle exports differently, here are two reliable ways to replicate this behavior:

Option 1: Default Import + Immediate Invocation

This is the cleanest approach, as we directly import the factory function (which is the module's default export) and call it:

// Import the factory function
import urlUnshortFactory from 'url-unshort';

// Invoke it to get the initialized utility object
const uu = urlUnshortFactory();

// Use it just like before
uu.expand('https://bit.ly/example')
  .then(longUrl => console.log('Expanded URL:', longUrl))
  .catch(err => console.error('Error expanding URL:', err));

Option 2: Using import * as (if you prefer this style)

If you use import * as, you'll get an object containing all exports from the module. The factory function will be under the default property, so you'll need to call that:

// Import all exports into a module object
import * as urlUnshortModule from 'url-unshort';

// Access the default export (the factory function) and invoke it
const uu = urlUnshortModule.default();

// Same usage as above
uu.expand('https://bit.ly/example')
  .then(longUrl => console.log('Expanded URL:', longUrl))
  .catch(err => console.error('Error expanding URL:', err));

Important Note for Node.js #

Make sure your project is configured to use ES6 modules:

• Add "type": "module" to your package.json file.
• If you're using a file extension, use .mjs instead of .js (though the package.json setting makes .js work for ES6 modules).

内容的提问来源于stack exchange，提问作者Cif