How to fix npm WARN old lockfile The package-lock.json file was created with an old version of npm in npm

# Regenerate lockfile without reinstalling
npm install --package-lock-only

# If that fails, try with legacy peer deps
npm install --package-lock-only --legacy-peer-deps

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

# Reinstall everything
npm install

# Create .nvmrc with your Node version
node -v > .nvmrc

# Team members can then run
nvm use

{
  "engines": {
    "node": ">=18.0.0",
    "npm": ">=9.0.0"
  }
}

# Write lockfileVersion 1 for npm v6 compatibility
npm install --lockfile-version=1

# Write lockfileVersion 2 (default for npm 7-8)
npm install --lockfile-version=2

# In CI/CD pipelines
npm ci