code: function ensureDOMElement (input) {
    let domElement = null
    let tmp = null
    if (input instanceof Element) {
      return input
    } else if ('string' == typeof input) {
      tmp = document.createElement('div')
      tmp.innerHTML = input
      domElement = tmp.innerHTML.length ? tmp.children[0] : new Template(input)
    } else {
      domElement = document.createElement('div')
    }
    return domElement
  }
docs: Ensure DOM element.
  
  @private
  @param {Mixed} input
  @return {Element}