listjoin.js

    // Join together lists that don't have
    // any blocks in-between
    {
      match: (node) => {
        return node.kind == 'document'
      },
      validate: (document) => {
        const joinableNode = document.nodes.find((node, key) => {
          if (!['ordered-list', 'unordered-list'].includes(node.type)) { return false }

          const previousNode = document.nodes.get(key - 1)
          if (!previousNode) { return false }

          return node.type === previousNode.type
        })

        if ( joinableNode ) {
          const previousNode = document.getPreviousSibling(joinableNode.key)
          return { previousNode, joinableNode }
        } else {
          return false
        }
      },
      normalize: (transform, document, nodes) => {
        const { joinableNode, previousNode } = nodes
        const joinableNodelistItems = joinableNode.nodes

        joinableNodelistItems.forEach((node, index) => {
          transform.moveNodeByKey(node.key, previousNode.key, previousNode.nodes.size + index)
        })
        return transform.removeNodeByKey(joinableNode.key)
      }
    }