setFieldOrder($cbUL) {
    if (!this.config.opts.sortableControls) {
      return false
    }
    const JSON = window.JSON

    const fieldOrder = []

    $cbUL.children().each((index, element) => {
      const type = $(element).data('type')
      if (type) {
        fieldOrder.push(type)
      }
    })

    if (storageAvailable('sessionStorage')) {
      window.sessionStorage.setItem('fieldOrder', JSON.stringify(fieldOrder))
    }
    return fieldOrder
  }
If user re-orders the elements their order should be saved.
@param {Object} $cbUL our list of elements
@return {Array|false} fieldOrder