const data = [
  {
    Domain: 'google.com',
    '# Reocurring Domains': 0
  },
  {
    Domain: 'apple.com',
    '# Reocurring Domains': 0
  },
  {
    Domain: 'facebook.com',
    '# Reocurring Domains': 0
  }
]

const domains = [
  {
    'google.com': true,
    'microsoft.com': true,
    'google.com': true
  },
  {
    'apple.com': true,
    'microsoft.com': true,
    'twitter.com': true
  },
  {
    'facebook.com': true,
    'apple.com': true,
    'facebook.com': true
  }
]
const domainIndex = {};
for (const entry of domains) {
	for(const domain of Object.keys(entry))
		domainIndex[domain] = (domainIndex[domain] || 0) +1	
}