javascript - ReferenceError: fetch is not defined - Stack Overflow

admin管理员组

文章数量:1125802

I have this error when I compile my code in node.js, how can I fix it?

RefernceError: fetch is not defined

This is the function I am doing, it is responsible for recovering information from a specific movie database.

function getMovieTitles(substr){  
  pageNumber=1;
  let url = '/?Title=' + substr + "&page=" + pageNumber;
  fetch(url).then((resp) => resp.json()).then(function(data) {
    let movies = data.data;
    let totPages = data.total_pages;
    let sortArray = [];
    for(let i=0; i<movies.length;i++){
        sortArray.push(data.data[i].Title);
     }
    for(let i=2; i<=totPages; i++){
           let newPage = i;
           let url1 = '/?Title=' + substr + "&page=" + newPage;

          fetch(url1).then(function(response) {
              var contentType = response.headers.get("content-type");
              if(contentType && contentType.indexOf("application/json") !== -1) {
                return response.json().then(function(json) {
                  //console.log(json); //uncomment this console.log to see the JSON data.

                 for(let i=0; i<json.data.length;i++){
                    sortArray.push(json.data[i].Title);
                 }

                 if(i==totPages)console.log(sortArray.sort());

                });
              } else {
                console.log("Oops, we haven't got JSON!");
              }
            });

        }
  })
  .catch(function(error) {
    console.log(error);
  });   
}

I have this error when I compile my code in node.js, how can I fix it?

RefernceError: fetch is not defined

This is the function I am doing, it is responsible for recovering information from a specific movie database.

function getMovieTitles(substr){  
  pageNumber=1;
  let url = 'https://jsonmock.hackerrank.com/api/movies/search/?Title=' + substr + "&page=" + pageNumber;
  fetch(url).then((resp) => resp.json()).then(function(data) {
    let movies = data.data;
    let totPages = data.total_pages;
    let sortArray = [];
    for(let i=0; i<movies.length;i++){
        sortArray.push(data.data[i].Title);
     }
    for(let i=2; i<=totPages; i++){
           let newPage = i;
           let url1 = 'https://jsonmock.hackerrank.com/api/movies/search/?Title=' + substr + "&page=" + newPage;

          fetch(url1).then(function(response) {
              var contentType = response.headers.get("content-type");
              if(contentType && contentType.indexOf("application/json") !== -1) {
                return response.json().then(function(json) {
                  //console.log(json); //uncomment this console.log to see the JSON data.

                 for(let i=0; i<json.data.length;i++){
                    sortArray.push(json.data[i].Title);
                 }

                 if(i==totPages)console.log(sortArray.sort());

                });
              } else {
                console.log("Oops, we haven't got JSON!");
              }
            });

        }
  })
  .catch(function(error) {
    console.log(error);
  });   
}

• javascript
• node.js

Share Improve this question Follow edited Jul 7, 2019 at 15:43 xaif 56366 silver badges2727 bronze badges asked Jan 25, 2018 at 0:22 jasa1704jasa1704 5,88933 gold badges1111 silver badges66 bronze badges 5

• 5 Welcome to SO, please provide the details on what have you tried so far? Please provide a Minimal, Complete, and Verifiable example wherever required. Also please take the time to read How to Ask – Pratibha Commented Jan 25, 2018 at 0:24
• 9 fetch is not a standard nodejs method - you need node-fetch – Jaromanda X Commented Jan 25, 2018 at 0:27
• 6 fetch() was designed for the browser and then back-ported to node.js in a third party module whcih you are apparently missing. The request() or request-promise() library is more natively built for node.js and supports a much wider range of options for node.js including streams, a zillion authentication methods, etc... – jfriend00 Commented Jan 25, 2018 at 0:41
• 1 Please, don’t include an image of your error. See: meta.stackoverflow.com/questions/285551/… – Étienne Miret Commented Jun 7, 2023 at 10:51
• Use node version >18 or install node-fetch – estani Commented Jun 28, 2024 at 9:25

Add a comment  | 

27 Answers 27

Sorted by: Reset to default 853

If you're using a version of Node prior to 18, the fetch API is not implemented out-of-the-box and you'll need to use an external module for that, like node-fetch.

Install it in your Node application like this

npm install node-fetch

then put the line below at the top of the files where you are using the fetch API:

import fetch from "node-fetch";

---

If your application cannot be updated to use ESM (aka import syntax), and you need to use CommonJS (aka require), then stick with v2 of node-fetch. As per their README, v2 will continue to receive critical bug fixes.

npm install node-fetch@2

and then this will work,

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

This is a quick dirty fix, please try to eliminate this usage in production code.

If fetch has to be accessible with a global scope

import fetch from 'node-fetch'
globalThis.fetch = fetch

You can use cross-fetch from @lquixada

Platform agnostic: browsers, node or react native

Install

npm install --save cross-fetch

Usage

With promises:

import fetch from 'cross-fetch';
// Or just: import 'cross-fetch/polyfill';

fetch('//api.github.com/users/lquixada')
  .then(res => {
    if (res.status >= 400) {
      throw new Error("Bad response from server");
    }
    return res.json();
  })
  .then(user => {
    console.log(user);
  })
  .catch(err => {
    console.error(err);
  });

With async/await:

import fetch from 'cross-fetch';
// Or just: import 'cross-fetch/polyfill';

(async () => {
  try {
    const res = await fetch('//api.github.com/users/lquixada');

    if (res.status >= 400) {
      throw new Error("Bad response from server");
    }

    const user = await res.json();

    console.log(user);
  } catch (err) {
    console.error(err);
  }
})();

If you want to avoid npm install and not running in browser, you can also use nodejs https module;

const https = require('https')
const url = "https://jsonmock.hackerrank.com/api/movies";
https.get(url, res => {
  let data = '';
  res.on('data', chunk => {
    data += chunk;
  });
  res.on('end', () => {
    data = JSON.parse(data);
    console.log(data);
  })
}).on('error', err => {
  console.log(err.message);
})

Starting node version 18, Fetch API is available (Stable in version 21.x) https://nodejs.org/docs/latest-v21.x/api/globals.html#fetch

// Promise version:

const url = "https://jsonmock.hackerrank.com/api/movies";

fetch(url).then(res => {
    return res.json();
}).then(data => {
    console.log('DATA: ', data);
})

OR

// async/await version

const url = "https://jsonmock.hackerrank.com/api/movies";

const getData = async () => {
    const response = await fetch(url);

    if (response.ok) {
        const data = await response.json();

        console.log('DATA: ', data);
    }
};
getData();

fetch came to Node v17 under experimental flag --experimental-fetch

It will be available in Node v18 without the flag.

https://github.com/nodejs/node/pull/41749#issue-1118239565

You no longer need any additional package to be installed

EDITED - New Solution

To use the latest version (3.0.0) you must do the import like this:

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

---

---

Old Anwser:

This may not be the best solution, but if you install this version :

npm install [email protected]

you can now use the line below without error's.

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

Node.js hasn't implemented the fetch() method, but you can use one of the external modules of this fantastic execution environment for JavaScript.

In one of the other answers, "node-fetch" is cited and that's a good choice.

In your project folder (the directory where you have the .js scripts) install that module with the command:

npm i node-fetch --save

Then use it as a constant in the script you want to execute with Node.js, something like this:

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

You should add this import in your file:

import * as fetch from 'node-fetch';

And then, run this code to add the node-fetch:
$ yarn add node-fetch

If you're working with typescript, then install node-fetch types:
$ yarn add @types/node-fetch

You have to use the isomorphic-fetch module to your Node project because Node does not contain Fetch API yet. For fixing this problem run below command:

npm install --save isomorphic-fetch es6-promise

After installation use below code in your project:

import "isomorphic-fetch"

For those also using typescript on node-js and are getting a ReferenceError: fetch is not defined error

npm install these packages:

    "node-fetch": "^2.3.0"

Then include:

import Global = NodeJS.Global;
export interface GlobalWithCognitoFix extends Global {
    fetch: any
}
declare const global: GlobalWithCognitoFix;
global.fetch = require('node-fetch');

Best one is Axios library for fetching. use npm i --save axios for installng and use it like fetch, just write axios instead of fetch and then get response in then().

It seems fetch support URL scheme with "http" or "https" for CORS request.

Install node fetch library npm install node-fetch, read the file and parse to json.

const fs = require('fs')
const readJson = filename => {
  return new Promise((resolve, reject) => {
    if (filename.toLowerCase().endsWith(".json")) {
      fs.readFile(filename, (err, data) => {
        if (err) {
          reject(err)
          return
        }
        resolve(JSON.parse(data))
      })
    }
    else {
      reject(new Error("Invalid filetype, <*.json> required."))
      return
    }
  })
}

// usage
const filename = "../data.json"
readJson(filename).then(data => console.log(data)).catch(err => console.log(err.message))

In HackerRank, some libraries are installed by default and some are not.

Because it is running Node.js, the fetch API is not installed by default.

The best thing for you to do is to check whether the libraries are or not installed.

on the top of the exercise, there is the following:

const https = require('https');

Please try to add this to the top as well:

const axios = require('axios');

and then run the code.

If there is a compilation error, then it's not available, otherwise you can use axios, which is a good alternative to fetch

To use it with then, you can:

function getMovieTitles(substr){
  axios.get(url)
    .then(function(response){
      console.log(response.data);
    })
}

or taking advantage of the async/await

async function getMovieTitles(substr){
  let response = await axios.get(url)
  console.log(response.data);
}

In node.js you can use : node-fetch package

npm i node-fetch

then :

import fetch from 'node-fetch';

here is a full sample in (nodejs) :

import fetch from "node-fetch";

const fetchData = async () => {
  const res = await fetch("https://restcountries.eu/rest/v2/alpha/col"); // fetch() returns a promise, so we need to wait for it

  const country = await res.json(); // res is now only an HTTP response, so we need to call res.json()

  console.log(country); // Columbia's data will be logged to the dev console
};

fetchData();

This is the related github issue This bug is related to the 2.0.0 version, you can solve it by simply upgrading to version 2.1.0. You can run npm i [email protected]

I encountered this error when I deployed my docker instance to production. It was weird to see the application failed with the error in this question.

I realised the Dockerfile had FROM node:16.13.1 and my system node version was 20.3.1.

If you don't want to use 'node-fetch' as shown in many answers and use 'fetch' ensure that you're using node version 18 or above. The reference error is likely because your node version is less than 18.

The following works for me in Node.js 12.x:

npm i node-fetch;

to initialize the Dropbox instance:

var Dropbox = require("dropbox").Dropbox;
var dbx = new Dropbox({
   accessToken: <your access token>,
   fetch: require("node-fetch")    
});

to e.g. upload a content (an asynchronous method used in this case):

await dbx.filesUpload({
  contents: <your content>,
  path: <file path>
});

This worked for me:

const nodeFetch = require('node-fetch') as typeof fetch;

npm i node-fetch 

Once installed, in your JavaScript file:

import fetch from "node-fetch";

Lastly make this change package.json file:

"type": "module"

For me these are looking more simple.

npm install node-fetch

import fetch from "node-fetch";

I got this error in a Jest test when using native fetch in Node.js version 18(.15.0).

Upgrading to the latest version of Jest (in my case from 27.5.1 to 29.5.0) fixed the issue:

npm install jest@latest

There are actually a lot of different libraries for making fetch available in the browser.

The main ones I'm aware of are:

• node-fetch
• cross-fetch
• whatwg-fetch
• isomorphic-fetch

I currently use node-fetch, and it has worked fine, but I don't really know which one is "the best". (though the openbase.com pages I linked to provide some metadata on usage [eg. Github stars, npm downloads], which can help)

fetch() can be used in the context of window so if you are a beginner as me and have this error when you try to compile a JavaScript file, just create an HTML file and add the script there, then you can open the browser’s terminal and there you should be able to see your requested resources

<!DOCTYPE html>
<html>
    <head></head>
    <body></body>
    <script>
        fetch('https://jsonplaceholder.typicode.com/posts/1')
        .then(response => response.json())
        .then(data => console.log(data))
    </script>
</html>

Solution without installations

Method 1

import { PLATFORM_ID } from '@angular/core';
import { isPlatformBrowser, isPlatformServer } from '@angular/common';

constructor(@Inject(PLATFORM_ID) private platformId: Object) { 
    // constructor code
}

ngOnInit() {
    if (isPlatformBrowser(this.platformId)) {
        // Client only code. Any javascript base functions
    }
    if (isPlatformServer(this.platformId)) {
        // Server only code. Any javascript base functions
    }
}

Method 2

import {  PLATFORM_ID} from '@angular/core';
    import { isPlatformBrowser } from '@angular/common';
    
    @Component({
      selector: 'app-navigation',
      templateUrl: './navigation.component.html',
      styleUrls: ['./navigation.component.scss'],
      changeDetection: ChangeDetectionStrategy.OnPush,
    })
    export class NavigationComponent implements OnInit {
      private isBrowser: boolean = false;
    
      constructor(
        @Inject(PLATFORM_ID) private platformId: Object
      ) {
        this.isBrowser = isPlatformBrowser(platformId);
      }
    
      ngOnInit(): void {
          if (this.isBrowser) {
            fetch('https://jsonplaceholder.typicode.com/posts/1')
                .then((response) => response.json())
                .then((json) => console.log(json));
            }
        }
      }

DEMO - JSFIDDLE - Open console to view the fetch api service working

Just make your app.js file Extension as app.mjs and the problem will be solved!!!:)

Might sound silly but I simply called npm i node-fetch --save in the wrong project. Make sure you are in the correct directory.

If need install:

npm install --save global-fetch

then

var fetch = require("node-fetch");

本文标签： javascriptReferenceError fetch is not definedStack Overflow