How should I import JSON in Node?

Question

I want to import package.json into test.js, both files are in same directory.

I tried with require :

const jsonfile = require("./packages.json");

console.log({ jsonfile });

it throws error:

file:///home/.../test.js:1
const jsonfile = require("./packages.json");
                 ^
ReferenceError: require is not defined
    at file:///home/.../test.js:1:18
    at ModuleJob.run (internal/modules/esm/module_job.js:145:37)
    at async Loader.import (internal/modules/esm/loader.js:182:24)
    at async Object.loadESM (internal/process/esm_loader.js:68:5)

This error implies, like it runs in browser, where is no require, I found an answer with similar message.

I tried with import:

import * as jsonfile from './packages.json';

console.log({ jsonfile });

internal/process/esm_loader.js:74
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/home/.../packages.json' imported from /home/.../test.js
    at finalizeResolution (internal/modules/esm/resolve.js:271:11)
    at moduleResolve (internal/modules/esm/resolve.js:694:10)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:784:11)
    at Loader.resolve (internal/modules/esm/loader.js:100:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:246:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:47:40)
    at link (internal/modules/esm/module_job.js:46:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

What I have tried more?

• Single quotes and double quote around filename
• filename with extension and without.
• with flag --experimental-json-modules
• adding "type":"module into package.json (but this is for Node >= 13, but without it I got warning (node:7170) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension. and then also error SyntaxError: Cannot use import statement outside a module)

I found even suggestions to load JSON-file as regular text files and parse them into data structure, but this seems like the last resort...

It seems such a trivial task, but I have not found the idiomatic way how to import JSON-data into Javascript variable. What is wrong here? How should I import it?

I use Node 12.21.0

Answer 1

You're using Node.js in ESM mode, ESM does not currently import JSON modules by default. You can either:

1. Turn on JSON module importing (by passing a CLI flag) OR
2. Create a require function in your ESM code and use that OR
3. JSON.parse the file manually

Turn on JSON module importing (by passing a CLI flag)

You can do that by passing the --experimental-json-modules flag.

node --experimental-json-modules yourfile.js # can import JSON here

Create a require function in your ESM code

You can also always fall back on CommonJS modules and create a require of your own:

import { createRequire } from 'module';
const require = createRequire(import.meta.url);
require('./package.json'); // now works

JSON.parse the file manually

You can always just read JSON files with regular filesystem methods:

# const fs = require('fs');
import * as fs from 'fs';
const result = JSON.parse(fs.readFileSync('./package.json'));