Added comments

src/server/routes/apiv3/pages.js

@@ -312,7 +312,10 @@ module.exports = (crowi) => {
       const PageTagRelation = mongoose.model('PageTagRelation');
       const ids = result.pages.map((page) => { return page._id });
       const relations = await PageTagRelation.find({ relatedPage: { $in: ids } }).populate('relatedTag');
+
+      // { pageId: [{ tag }, ...] }
       const relationsMap = new Map();
+      // increment relationsMap
       relations.forEach((relation) => {
         const pageId = relation.relatedPage.toString();
         if (!relationsMap.has(pageId)) {
@@ -320,6 +323,7 @@ module.exports = (crowi) => {
         }
         relationsMap.get(pageId).push(relation.relatedTag);
       });
+      // add tags to each page
       result.pages.forEach((page) => {
         const pageId = page._id.toString();
         page.tags = relationsMap.has(pageId) ? relationsMap.get(pageId) : [];