basic snapshot implementation

src/index.ts

@@ -0,0 +1,138 @@
+let _id = 1;
+
+function genId(): number {
+  return _id++;
+}
+
+enum NodeType {
+  Document,
+  DocumentType,
+  Element,
+  Text,
+  CDATA,
+  Comment,
+}
+
+type serializedNode =
+  | documentNode
+  | documentTypeNode
+  | elementNode
+  | textNode
+  | cdataNode
+  | commentNode;
+
+type documentNode = {
+  type: NodeType.Document;
+  childNodes: serializedNode[];
+};
+
+type documentTypeNode = {
+  type: NodeType.DocumentType;
+  name: string;
+  publicId: string;
+  systemId: string;
+};
+
+type attributes = {
+  [key: string]: string;
+};
+type elementNode = {
+  type: NodeType.Element;
+  tagName: string;
+  attributes: attributes;
+  childNodes: serializedNode[];
+};
+
+type textNode = {
+  type: NodeType.Text;
+  textContent: string;
+};
+
+type cdataNode = {
+  type: NodeType.CDATA;
+  textContent: '';
+};
+
+type commentNode = {
+  type: NodeType.Comment;
+  textContent: string;
+};
+
+function serializeNode(n: Node): serializedNode | false {
+  switch (n.nodeType) {
+    case n.DOCUMENT_NODE:
+      return {
+        type: NodeType.Document,
+        childNodes: [],
+      };
+    case n.DOCUMENT_TYPE_NODE:
+      return {
+        type: NodeType.DocumentType,
+        name: (n as DocumentType).name,
+        publicId: (n as DocumentType).publicId,
+        systemId: (n as DocumentType).systemId,
+      };
+    case n.ELEMENT_NODE:
+      const tagName = (n as HTMLElement).tagName.toLowerCase();
+      const attributes: attributes = {};
+      for (const { name, value } of Array.from((n as HTMLElement).attributes)) {
+        attributes[name] = value;
+      }
+      return {
+        type: NodeType.Element,
+        tagName,
+        attributes,
+        childNodes: [],
+      };
+    case n.TEXT_NODE:
+      // The parent node may not be a html element which has a tagName attribute.
+      // So just let it be undefined which is ok in this use case.
+      const parentTagName =
+        n.parentNode && (n.parentNode as HTMLElement).tagName;
+      let textContent = (n as Text).textContent;
+      if (parentTagName === 'SCRIPT') {
+        textContent = '';
+      }
+      return {
+        type: NodeType.Text,
+        textContent,
+      };
+    case n.CDATA_SECTION_NODE:
+      return {
+        type: NodeType.CDATA,
+        textContent: '',
+      };
+    case n.COMMENT_NODE:
+      return {
+        type: NodeType.Comment,
+        textContent: (n as Comment).textContent,
+      };
+    default:
+      return false;
+  }
+}
+
+type serializedNodeWithId = serializedNode & { id: number };
+
+function snapshot(n: Node): serializedNodeWithId | null {
+  const _serializedNode = serializeNode(n);
+  if (!_serializedNode) {
+    // TODO: dev only
+    console.warn(n, 'not serialized');
+    return null;
+  }
+  const serializedNode: serializedNodeWithId = Object.assign(_serializedNode, {
+    id: genId(),
+  });
+  if (
+    serializedNode.type === NodeType.Document ||
+    serializedNode.type === NodeType.Element
+  ) {
+    for (const childN of Array.from(n.childNodes)) {
+      serializedNode.childNodes.push(snapshot(childN));
+    }
+  }
+  return serializedNode;
+}
+
+export default snapshot;