dist/vue-inview.js
function (el) {
  this.el = el
  if(typeof el.classList !== 'undefined') {
    // if classList support
    this.old = false
  } else {
    // browser class unsupport classList
    this.classList = new nativeClasList(el)
    this.old = true
  }
}
function (el) {
  this.el = el
  if(typeof el.classList !== 'undefined') {
    // if classList support
    this.old = false
  } else {
    // browser class unsupport classList
    this.classList = new nativeClasList(el)
    this.old = true
  }
}
define classList object