index.js

const data1 = {
  attributes: {
    domain: 'from.attributes.com'
  }
}

const data2 = {
  attributes: {
    unknownAttributes: {
      domain: 'from.unknownAttributes.com'
    }
  }
}

const data3 = {
  attributes: {
    url:
      'https://www.fromurl.com/Zinus-SmartBase-Foundation-Replacement-Noise-Free/dp/B01GHHIWFO/ref=sr_1_1/146-9491966-1844353?ie=UTF8&qid=1521436930&sr=8-1&keywords=841550091137'
  }
}

function getDomain(attributes) {
  if (!attributes) {
    return null
  }

  if (attributes) {
    if (attributes.domain) {
      return attributes.domain
    }
    const unknownAttributes = attributes.unknownAttributes
    if (unknownAttributes) {
      if (unknownAttributes.domain) {
        return unknownAttributes.domain
      }
    }
    const url = attributes.url
    if (url) {
      // const match = url
      //   .replace(/^(https?:)/i, '')
      //   .replace(/(www[0-9]?\.)/i, '')
      //   .split('/')
      // return match[2]
      const match = url.match(/:\/\/(www[0-9]?\.)?(.[^\/:]+)/i)
      if (match !== null && match.length > 2 && typeof match[2] === "string" && match[2].length > 0) {
        return match[2]
      } else {
        return null
      }
    }
  }
}

console.log(getDomain(null))
console.log(getDomain(undefined))

console.log(getDomain(data1.attributes))

console.log(getDomain(data2.attributes))

console.log(getDomain(data3.attributes))

create or replace function getDomain1(v variant)
    returns string
    language javascript
    as '
function getDomain1(attributes) {
  if (!attributes) {
    return null
  }

  if (attributes) {
    if (attributes.domain) {
      return attributes.domain
    }
    const unknownAttributes = attributes.unknownAttributes
    if (unknownAttributes) {
      if (unknownAttributes.domain) {
        return unknownAttributes.domain
      }
    }
    const url = attributes.url
    if (url) {
      const match = url.match(/:\/\/(www[0-9]?\.)?(.[^\/:]+)/i)
      if (match !== null && match.length > 2 && typeof match[2] === "string" && match[2].length > 0) {
        return match[2]
      } else {
        return null
      }
    }
  }
}
return getDomain1(V)
';

JavaScript compilation error: Uncaught SyntaxError: 
  Unexpected token . in GETDOMAIN1 at ' const match = url.match(/://(www[0-9]?.)?(.[^/:]+)/i)' position 44

Regex details: https://regex101.com/r/fyZuSt/1