add placeholder extension

packages/tiptap-extensions/src/extensions/Placeholder.js

@@ -0,0 +1,39 @@
+import { Extension, Plugin } from 'tiptap'
+import { Decoration, DecorationSet } from 'prosemirror-view'
+
+export default class PlaceholderExtension extends Extension {
+
+	get name() {
+		return 'placeholder'
+	}
+
+	get defaultOptions() {
+		return {
+			emptyNodeClass: 'is-empty',
+		}
+	}
+
+	get plugins() {
+		return [
+			new Plugin({
+				props: {
+					decorations: state => {
+						const decorations = []
+
+						state.doc.descendants((node, pos) => {
+							if (node.type.isBlock && node.childCount === 0) {
+								const decoration = Decoration.node(pos, pos + node.nodeSize, {
+									class: this.options.emptyNodeClass,
+								})
+								decorations.push(decoration)
+							}
+						})
+
+						return DecorationSet.create(state.doc, decorations)
+					},
+				},
+			}),
+		]
+	}
+
+}