Show data Table with pagination (startRow, endRow, filter, sorting)

server/classes/queryclass.js

@@ -0,0 +1,76 @@
+
+class CParamsQuery {
+  constructor(params) {
+    this.startRow = params.startRow;
+    this.endRow = params.endRow;
+    // this.count = params.count;
+    this.filter = params.filter;
+    this.sortBy = params.sortBy;
+    this.descending = params.descending;
+  }
+
+}
+
+/**
+ * Query blog posts by user -> paginated results and a total count.
+ * @param userId {ObjectId} ID of user to retrieve blog posts for
+ * @param startRow {Number} First row to return in results
+ * @param endRow {Number} Last row to return in results
+ * @param [filter] {Object} Optional extra matching query object
+ * @param [sort] {Object} Optional sort query object
+ * @returns {Object} Object -> `{ rows, count }`
+ */
+
+function queryBlogPostsByUser (userId, startRow, endRow, filter = {}, sort = false) {
+  const User = this;
+
+  if (!(user instanceof mongoose.Types.ObjectId)) {
+    throw new Error('userId must be ObjectId')
+  } else if (typeof startRow !== 'number') {
+    throw new Error('startRow must be number')
+  } else if (typeof endRow !== 'number') {
+    throw new Error('endRow must be number')
+  }
+
+  const query = [
+    // more lookups go here if you need them
+    // we have a many-to-one from blogPost -> user
+    { $lookup: {
+        from: 'users',
+        localField: 'user',
+        foreignField: '_id',
+        as: 'user'
+      } },
+    // each blog has a single user (author) so flatten it using $unwind
+    { $unwind: '$user' },
+    // filter the results by our userId
+    { $match: Object.assign({ 'user._id': userId }, filter) }
+  ];
+
+  if (sort) {
+    // maybe we want to sort by blog title or something
+    query.push({ $sort: sort })
+  }
+
+  query.push(
+    { $group: {
+        _id: null,
+        // get a count of every result that matches until now
+        count: { $sum: 1 },
+        // keep our results for the next operation
+        results: { $push: '$$ROOT' }
+      } },
+    // and finally trim the results to within the range given by start/endRow
+    { $project: {
+        count: 1,
+        rows: { $slice: ['$results', startRow, endRow] }
+      } }
+  );
+
+  return User
+    .aggregate(query)
+    .then(([{ count, rows }]) => ({ count, rows }))
+};
+
+
+module.exports = { CParamsQuery, queryBlogPostsByUser };