I am doing nothing to trigger this error. The app works fine one second, and doesn't the next.

Why is this happening? It is not due to the missing @rollup/plugin-json plugin because it worked previously without it.

Error

 path (imported by path?commonjs-external) http (imported by http?commonjs-external) net (imported by net?commonjs-external) url (imported by url?commonjs-external) [!] Error: Unexpected token (Note that you need @rollup/plugin-json to import JSON files) node_modules/mime-db/db.json (2:40) 1: { 2: "application/1d-interleaved-parityfec": { ^ 3: "source": "iana" 4: }, Error: Unexpected token (Note that you need @rollup/plugin-json to import JSON files) at error (/mnt/c/ivan/dev/lab/atlas-biotek/node_modules/rollup/dist/shared/rollup.js:5265:30) at Module.error (/mnt/c/ivan/dev/lab/atlas-biotek/node_modules/rollup/dist/shared/rollup.js:9835:16) at tryParse (/mnt/c/ivan/dev/lab/atlas-biotek/node_modules/rollup/dist/shared/rollup.js:9716:23) at Module.setSource (/mnt/c/ivan/dev/lab/atlas-biotek/node_modules/rollup/dist/shared/rollup.js:10142:19) at ModuleLoader.addModuleSource (/mnt/c/ivan/dev/lab/atlas-biotek/node_modules/rollup/dist/shared/rollup.js:18312:20) 

Adding the plugin

npm i @rollup/plugin-json --save-dev 

rollup.js.config

import json from "@rollup/plugin-json"; export default { plugins: [ commonjs(), json(), // <---- put after commonjs ] } 

Client error

Uncaught ReferenceError: require$$0$1 is not defined at main.js:5 (anonymous) @ main.js:5 

2 Answers

If you are using typescript, I added the json() plugin after typescript:

File: rollup.config.js

import typescript from "rollup-plugin-typescript2"; import resolve from "@rollup/plugin-node-resolve"; import commonjs from "@rollup/plugin-commonjs"; import replace from "@rollup/plugin-replace"; import json from "@rollup/plugin-json"; const plugins = [ typescript({ tsconfig: "./tsconfig-build.json", }), json(), <<------------- HERE resolve(), commonjs(), replace({ ... preventAssignment: true, }), ]; 

The problem was that I was importing a node module in the client due to autocomplete.

import { is } from "express/lib/request";