Using import fs from 'fs'

问题

I want to use import fs from 'fs' in JavaScript. Here is a sample:

import fs from 'fs'

var output = fs.readFileSync('someData.txt')

console.log(output)

The error I get when I run my file using node main.js is:

(function (exports, require, module, __filename, __dirname) { import fs from 'fs
'
                                                              ^^^^^^
SyntaxError: Unexpected token import

What should I install in node in order to achieve importing modules and functions from other places?

回答1:

ES6 modules support in node.js is fairly recent; even in the bleeding-edge versions, it is still experimental. With node 10, you can start node with the --experimental-modules flag, and it will likely work.

To import on older node versions - or standard node 10 - use CommonJS syntax:

const fs = require('fs');

回答2:

For default exports you should use:

import * as fs from 'fs';

Or in case the module has named exports:

import {fs} from 'fs';

Example:

//module1.js

export function function1() {
  console.log('f1')
}

export function function2() {
  console.log('f2')
}

export default function1;

And then:

import defaultExport, { function1, function2 } from './module1'

defaultExport();  // This calls function1
function1();
function2();

Additionally, you should use webpack or something similar to be able to use es6 import

回答3:

In order to use import { readFileSync } from 'fs', you have to:

Be using node 10+
Use the --experimental-modules flag (in node 10), e.g. node --experimental-modules server.mjs (see #3 for explanation of .mjs)
Rename the file extension of your file with the import statements, to .mjs, .js will not work, e.g. server.mjs

The other answers hit on 1 and 2, but 3 is also necessary. Also, note that this feature is considered extremely experimental at this point (1/10 stability) and not recommended for production, but I will still probably use it.

Here's the node 10 ESM documentation

回答4:

Building on RobertoNovelo's answer:

import * as fs from 'fs';

is currently the simplest way to do it.

Tested with a node project (node v10.15.3), with esm (https://github.com/standard-things/esm#readme) allowing to use import.

回答5:

The new ECMAScript module support is able natively in Node.js 12 🎉

It was released yesterday (2019-04-23) and it means there is no need to use the flag --experimental-modules.

To read more about it: http://2ality.com/2019/04/nodejs-esm-impl.html

回答6:

If we are using TypeScript, we can update the Type definition file by running the command npm install @types/node from the terminal/command prompt.

回答7:

It's not supported just yet.... If you want to use you will have to install babel

https://babeljs.io/docs/setup/

来源：https://stackoverflow.com/questions/43622337/using-import-fs-from-fs

标签

javascript

es6-modules