Error "SyntaxError: Cannot use import statement outside a module" when deploying React app with Netlify Functions

Question

I deployed an app using Netlify Functions and got an error ""errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module"". How can I solve this?

I used create-react-app to make the app. I installed node-fetch and used in the Netlify Functions. I didn't install Lambda. I've tried adding "type": "module" in package.json but it didn't work

■Error on Netlify Functions Log

6:58:51 PM: 2021-09-15T09:58:51.177Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
6:58:51 PM: 2021-09-15T09:58:51.372Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
6:58:51 PM: 75585d70 Duration: 159.55 ms    Memory Usage: 14 MB 6:58:51 PM: Unknown application error occurred
Runtime.UserCodeSyntaxError
6:59:05 PM: 2021-09-15T09:59:05.638Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
6:59:05 PM: 2f6dbc1c Duration: 135.91 ms    Memory Usage: 14 MB 6:59:05 PM: Unknown application error occurred
Runtime.UserCodeSyntaxError
6:59:05 PM: 2021-09-15T09:59:05.845Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
6:59:23 PM: 2021-09-15T09:59:23.733Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
6:59:23 PM: 7b7c0366 Duration: 135.01 ms    Memory Usage: 14 MB 6:59:23 PM: Unknown application error occurred
Runtime.UserCodeSyntaxError
6:59:23 PM: 2021-09-15T09:59:23.928Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Cannot use import statement outside a module","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module","    at _loadUserApp (/var/runtime/UserFunction.js:98:13)","    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}

■package.json

{
  "type": "module",
  "homepage": "http://.",
  "name": "react-weather-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^5.14.1",
    "@testing-library/react": "^11.2.7",
    "@testing-library/user-event": "^12.8.3",
    "node-fetch": "^3.0.0",
    "react": "^17.0.2",
    "react-dom": "^17.0.2",
    "react-icons": "^4.2.0",
    "react-scripts": "4.0.3",
    "web-vitals": "^1.1.2"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "predeploy": "npm run build",
    "deploy": "gh-pages -d build"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "devDependencies": {
    "gh-pages": "^3.2.3"
  }

■Netlify Functions

import fetch from 'node-fetch';

exports.handler = async function(event) {
    try{
        const {city} = event.queryStringParameters;
        const API = process.env.REACT_APP_API_KEY;

        const url= `https://api.openweathermap.org/data/2.5/weather?q=${city}&appid=${API}`;

        const response = await fetch(url);
        const data = await response.json();
        console.log(data);
        return { 
            statusCode: 200,
            body: JSON.stringify({data})
        }
    } catch(err) {
        console.log(err);
        return { 
            statusCode: 400,
            body: JSON.stringify({error: 'Failed fetching data'})
        }
    }
}

Answer 1

将 Netlify Functions 的文件扩展名从*.js更改为*.mjs以使用import语句。

Answer 2

Alternatives to Maksim Shamihulau's answer based on the docs and netlify forum :

1. Use CommonJs fetch function instead

rewrite

import fetch from 'node-fetch';

as

const fetch = (...args) => import('node-fetch').then(({default: fetch}) => fetch(...args));

2. Use node-fetch@2 (see forum post ) with require

as

const fetch = require('node-fetch');

Overall, the file extension rewrite method by Maksim Shamihulau seems superior to both.