custom-shallow-equal.ts

function isRecord(record): boolean {
  // Could be improved, perhaps with use of a Symbol:
  return record && record._id && (typeof record._id)=="string"
}

function isSimple(obj): boolean {
  return !obj || isRecord(obj) || (typeof obj)!="object"
}

function shallowEqual(objA: any, objB: any): boolean {
  const simpleComparison = isSimple(objA) || isSimple(objB)

  if (simpleComparison) {
    return objA === objB
  }

  if (Array.isArray(objA) && Array.isArray(objB)) {
    if (objA.length !== objB.length) return false
    return objA.every((e, i)=>
      objB[i] === e
    )
  }

  if (typeof objA == 'object' && typeof objB == 'object') {
    const keysA = Object.keys(objA)
    const keysB = Object.keys(objB)
  
    if (keysA.length !== keysB.length) return false

    return keysA.every(key=>
      objA[key] === objB[key]
    )
  }

  return false
}

export default shallowEqual