Flatten from a DOM Node included childNodes nested to a flat array.

convertNodeToFlattenArray.js

var r = []
const flatten = (a) => {
  if (a.firstChild === null) {
    r.push(a)
  }
  else if (a.childNodes.length > 0) {
    var c = a.childNodes
    Array.from(c).forEach(function (v) {
        if (v.firstChild === null) {
          r.push(v)
        }
        else {
          flatten.apply(this, [v])
        }
    })
  }
  return r
}