dist/vue-inview.js
function (v) {
  var result = 0
  var key
  for (key in v) {
      v.hasOwnProperty(key) && result++
  }
  return result
}
function (v) {
  var result = 0
  var key
  for (key in v) {
      v.hasOwnProperty(key) && result++
  }
  return result
}
return number
- counting key of object