_createDomTree () {
    const dom = this.dom
    const domTree = document.createElement('table')
    const tbody = document.createElement('tbody')
    domTree.style.borderCollapse = 'collapse' // TODO: put in css
    domTree.className = 'jsoneditor-values'
    domTree.appendChild(tbody)
    const tr = document.createElement('tr')
    tbody.appendChild(tr)

    // create expand button
    const tdExpand = document.createElement('td')
    tdExpand.className = 'jsoneditor-tree'
    tr.appendChild(tdExpand)
    dom.expand = this._createDomExpandButton()
    tdExpand.appendChild(dom.expand)
    dom.tdExpand = tdExpand

    // create the field
    const tdField = document.createElement('td')
    tdField.className = 'jsoneditor-tree'
    tr.appendChild(tdField)
    dom.field = this._createDomField()
    tdField.appendChild(dom.field)
    dom.tdField = tdField

    // create a separator
    const tdSeparator = document.createElement('td')
    tdSeparator.className = 'jsoneditor-tree'
    tr.appendChild(tdSeparator)
    if (this.type !== 'object' && this.type !== 'array') {
      tdSeparator.appendChild(document.createTextNode(':'))
      tdSeparator.className = 'jsoneditor-separator'
    }
    dom.tdSeparator = tdSeparator

    // create the value
    const tdValue = document.createElement('td')
    tdValue.className = 'jsoneditor-tree'
    tr.appendChild(tdValue)
    dom.value = this._createDomValue()
    tdValue.appendChild(dom.value)
    dom.tdValue = tdValue

    return domTree
  }
Create a DOM tree element, containing the expand/collapse button
@return {Element} domTree
@private