How to fix npm ERR! missing script: 'build' in Node.js

Run npm run without any arguments to see all currently defined scripts:

npm run

This will display a complete list of available scripts. Check if the script you're trying to run is listed. If it's not there, you need to add it.

Ensure you're running the command from your project's root directory where package.json is located:

# Verify package.json exists
ls package.json

# Or view its contents
cat package.json

If package.json is not in the current directory, navigate to the correct location using cd.

Open package.json and add the script to the "scripts" object. For example, to add a build script:

{
  "name": "your-project",
  "version": "1.0.0",
  "scripts": {
    "start": "node index.js",
    "build": "webpack --mode production",
    "test": "jest"
  }
}

Common script definitions:
- build: "webpack" or "react-scripts build" or "tsc"
- dev: "nodemon index.js" or "next dev"
- start: "node index.js" or "next start"
- test: "jest" or "mocha"

The exact command depends on your project's build tool and framework.

Search your package.json for multiple "scripts" objects. If you find more than one, merge them into a single section:

Incorrect (duplicate scripts):

{
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {...},
  "scripts": {
    "build": "webpack"
  }
}

Correct (merged):

{
  "scripts": {
    "start": "node index.js",
    "build": "webpack"
  },
  "dependencies": {...}
}

JSON objects cannot have duplicate keys; the second one overwrites the first.

Check that your package.json is valid JSON with no syntax errors:

# Use Node.js to validate
node -e "console.log(JSON.parse(require('fs').readFileSync('package.json', 'utf8')))"

Or use an online JSON validator. Common issues include:
- Missing commas between properties
- Trailing commas after the last property
- Unescaped quotes in string values
- Missing closing braces or brackets

If the file is corrupted, restore it from version control or regenerate it.

If you've made changes to package.json or suspect corruption, reinstall dependencies:

# Remove existing installations
rm -rf node_modules package-lock.json

# Reinstall
npm install

This ensures npm has the latest configuration and all dependencies are properly installed.