Node.js require与React.js import缓存机制是否一致？多变量导入缓存疑问

Great question! This is a common point of confusion between CommonJS (Node.js's require) and ES Modules (which React uses via import), so let's break it down clearly.

Core Answer #

Yes, React's import mechanism behaves similarly to Node.js's require when it comes to caching: modules are loaded and executed only once, and all subsequent imports reuse the in-memory exports instead of reprocessing the module file.

How It Works in Node.js (CommonJS) #

For Node.js's require:

• The first time you load a module, Node reads the file, executes its code, and stores the exported object in the require.cache object.
• Any subsequent require calls for the same module path skip reading the file and re-running code—they pull directly from this cache.

How It Works in React (ES Modules) #

React relies on ES Modules (import/export syntax), which have a standardized caching system that works across browsers and bundlers (like Webpack, Vite, or Rollup—tools almost all React apps use):

• The first time an import references a module, the module is resolved (bundler) or fetched (browser), executed, and its exports are stored in an internal module cache.
• Every subsequent import (even if you're importing different functions/variables from the same module) will reuse that cached instance. No re-reading the file or re-running module code occurs.

Example to Prove It #

Let's use a simple utility module to demonstrate:

// utils.js
console.log("Module executed!");

export const greeting = "Hello React!";
export function multiply(a, b) { return a * b; }

Now import from this module in two separate React components:

// ComponentA.jsx
import { greeting } from './utils.js';
function ComponentA() {
  return <div>{greeting}</div>;
}

// ComponentB.jsx
import { multiply } from './utils.js';
function ComponentB() {
  return <div>{multiply(4, 5)}</div>;
}

When you run your app, you'll only see Module executed! logged once—even though we imported from utils.js twice. This confirms the module was only executed once, and both components use the cached exports.

Dynamic import() Behavior #

Even dynamic import() calls follow this caching rule. If you call import('./utils.js') multiple times, the first call loads and executes the module; all subsequent calls return a resolved Promise pointing to the already cached module.

Key Distinction (For Context) #

The only minor difference between CommonJS and ES Module caching is the cache key:

• CommonJS uses the module's file path as the cache key.
• ES Modules use the module's URL (in browsers) or a bundler-generated module ID (in bundled React apps).

For everyday React development, this distinction rarely matters—any import of the same file (relative to your project structure) will hit the cache.

内容的提问来源于stack exchange，提问作者Or Assayag