package.json 和文件扩展名
🌐 package.json and file extensions
在一个包中，package.json "type" 字段定义了 Node.js 应该如何解释 .js 文件。如果 package.json 文件没有 "type" 字段，.js 文件将被视为 CommonJS。
🌐 Within a package, the package.json "type" field defines how
Node.js should interpret .js files. If a package.json file does not have a
"type" field, .js files are treated as CommonJS.
'package.json' '类型''的'“模块”值告诉Node.js解释“.js” 该包内的文件使用ES 模块语法。
🌐 A package.json "type" value of "module" tells Node.js to interpret .js
files within that package as using ES module syntax.
"type" 字段不仅适用于初始入口点 (node my-app.js)，还适用于通过 import 语句和 import() 表达式引用的文件。
🌐 The "type" field applies not only to initial entry points (node my-app.js)
but also to files referenced by import statements and import() expressions.
// my-app.js, treated as an ES module because there is a package.json
// file in the same folder with "type": "module".
import './startup/init.js';
// Loaded as ES module since ./startup contains no package.json file,
// and therefore inherits the "type" value from one level up.
import 'commonjs-package';
// Loaded as CommonJS since ./node_modules/commonjs-package/package.json
// lacks a "type" field or contains "type": "commonjs".
import './node_modules/commonjs-package/index.js';
// Loaded as CommonJS since ./node_modules/commonjs-package/package.json
// lacks a "type" field or contains "type": "commonjs". 以 .mjs 结尾的文件总是作为 ES 模块 加载，无论最近的父级 package.json 是什么。
🌐 Files ending with .mjs are always loaded as ES modules regardless of
the nearest parent package.json.
以 .cjs 结尾的文件总是作为 CommonJS 加载，无论最近的父级 package.json 是什么。
🌐 Files ending with .cjs are always loaded as CommonJS regardless of the
nearest parent package.json.
import './legacy-file.cjs';
// Loaded as CommonJS since .cjs is always loaded as CommonJS.
import 'commonjs-package/src/index.mjs';
// Loaded as ES module since .mjs is always loaded as ES module. .mjs 和 .cjs 扩展名可以在同一个包中混合使用不同类型：
🌐 The .mjs and .cjs extensions can be used to mix types within the same
package: