Please verify that the package.json has a valid "main" entry

# Table of Contents

1. Please verify that the package.json has a valid "main" entry
2. Delete your node_modules and package-lock.json files
3. Setting the correct main property in your package.json file
4. Issue the npm update command
5. Using Firebase functions with TypeScript

# Please verify that the package.json has a valid "main" entry

The error "Please verify that the package.json has a valid "main" entry" occurs for 3 main reasons:

1. Having a glitched node_modules directory.
2. Incorrectly setting the main property in your package.json file.
3. Incorrectly setting the main property when writing Firebase functions in TypeScript.

To solve the error, delete package-lock.json and node_modules and reinstall your dependencies.

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Error: Cannot find module '/home/borislav/Documents/react-project/node_modules/package/index.js'.
Please verify that the package.json has a valid "main" entry

# Delete your node_modules and package-lock.json files

The error often occurs when your node_modules directory glitches.

This might happen if you start installing a module and press Ctrl + C to stop the command midway through.

On macOS or Linux, issue the following commands in bash or zsh.

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# 👇️  (macOS/Linux) delete node_modules and package-lock.json
rm -rf node_modules
rm -f package-lock.json
rm -f yarn.lock

# 👇️ clean your npm cache
npm cache clean --force

# 👇️ install packages
npm install

On Windows, issue the following commands in CMD.

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# 👇️  (Windows) delete node_modules and package-lock.json
rd /s /q "node_modules"
del package-lock.json
del -f yarn.lock

# 👇️ clean your npm cache
npm cache clean --force

# 👇️ install packages
npm install

The commands delete your node_modules directory and your package-lock.json files and regenerate them with the npm install command.

If the error persists, restart your code editor.

# Setting the correct main property in your package.json file

Make sure the main property in your package.json file points to the entry point of your application, e.g. index.js.

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{
  "main": "index.js",
  "scripts": {
    "dev": "nodemon index.js"
  }
}

The main property is the primary entry point to your program.

Notice that my dev script issues the nodemon index.js command because the index.js file is the entry point of my Node.js application.

The main property has to be set to a module relative to the root directory (relative to where package.json is located).

If the main property is not set, it defaults to index.js in the root folder.

# Issue the npm update command

If the error persists, try to issue the npm update command.

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npm update

The npm update command installs missing packages and updates the existing packages respecting semver.

If the command fails, rerun it with the --force flag.

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npm update --force

If you still get the error, try to run the npm audit fix command.

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npm audit fix --force

The npm audit fix command finds packages with vulnerabilities and applies remediations.

# Using Firebase functions with TypeScript

If you use Firebase functions with TypeScript, verify where the index.js file gets generated.

Open your package.json file and set the main property to the entry point index.js file.

Your entry point file might be functions/lib/index.js (specified relative to the package.json file location).

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{
  "main": "functions/lib/index.js",
  "scripts": {
    // ....
  },
}

After you set the main property correctly, open your terminal in the functions directory and issue the npm run build command.

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# from the functions/ directory
npm run build

The command will convert your .ts file to .js files.

Check the contents of your lib directory and verify that the path to the built .js files is correct.

The main property has to point to the js file that is produced when you run the npm run build command.

# Restart your Code Editor

If the error persists, try to restart your code editor.

Restarting your IDE often helps, especially when the error is shown in the ESLint extension.