不幸的是，Node.js还不支持ES6的导入。

要完成您要做的事情(导入Express模块)，这段代码应该足够了

var express = require("express");

另外，确保通过运行安装了Express

$ npm install express

有关学习Node.js的更多信息，请参阅Node.js文档。

作为Node.js v12(这可能是相当稳定的现在，但仍然标记为“实验”)，你有两个选项使用ESM (ECMAScript模块)在Node.js(文件，有第三种方法计算字符串)，以下是文档所说的:

The --experimental-modules flag can be used to enable support for ECMAScript modules (ES modules). Once enabled, Node.js will treat the following as ES modules when passed to node as the initial input, or when referenced by import statements within ES module code: Files ending in .mjs. Files ending in .js, or extensionless files, when the nearest parent package.json file contains a top-level field "type" with a value of "module". Strings passed in as an argument to --eval or --print, or piped to node via STDIN, with the flag --input-type=module. Node.js will treat as CommonJS all other forms of input, such as .js files where the nearest parent package.json file contains no top-level "type" field, or string input without the flag --input-type. This behavior is to preserve backward compatibility. However, now that Node.js supports both CommonJS and ES modules, it is best to be explicit whenever possible. Node.js will treat the following as CommonJS when passed to node as the initial input, or when referenced by import statements within ES module code: Files ending in .cjs. Files ending in .js, or extensionless files, when the nearest parent package.json file contains a top-level field "type" with a value of "commonjs". Strings passed in as an argument to --eval or --print, or piped to node via STDIN, with the flag --input-type=commonjs.

如果你可以使用'babel'，试着在package.json(——presets=es2015)中添加构建脚本，如下所示。它可以预编译导入代码到es2015

"build": "babel server --out-dir build --presets=es2015 && webpack"

错误:SyntaxError:未预期的令牌导入或SyntaxError:未预期的令牌导出

解决方案:以更改所有导入为例

const express               = require('express');
const webpack               = require('webpack');
const path                  = require('path');
const config                = require('../webpack.config.dev');
const open                  = require('open');

同时修改export default = foo;模块。出口= foo;

在我的情况下，它是看着.babelrc文件，它应该包含这样的东西:

{
  "presets": ["es2015-node5", "stage-3"],
  "plugins": []
}

我很惊讶esm竟然没有被提到。这个小但功能强大的包允许您使用import或require。

在项目中安装esm

$ NPM install——保存esm

更新您的节点启动脚本以使用esm

Node -r esm app.js

Esm就是管用。我在.mjs和——experimental-modules上浪费了大量的时间，却发现.mjs文件不能导入使用require或module.exports的文件。这是一个大问题，而esm允许你混合和匹配，它只是解决它…Esm就是管用。