Update docs of mongodb BulkWriteResult type (#43855)

* Update docs of mongodb BulkWriteResult type

* Update index.d.ts

types/mongodb/index.d.ts

@@ -30,6 +30,7 @@
 //                 Piotr Błażejewicz <https://github.com/peterblazejewicz>
 //                 Linus Unnebäck <https://github.com/LinusU>
 //                 Richard Bateman <https://github.com/taxilian>
+//                 Igor Strebezhev <https://github.com/xamgore>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 3.0
 
@@ -1851,24 +1852,78 @@ export interface BulkWriteResultUpsertedIdObject {
     _id: ObjectId;
 }
 
-/** http://mongodb.github.io/node-mongodb-native/3.1/api/BulkWriteResult.html */
+/** http://mongodb.github.io/node-mongodb-native/3.5/api/BulkWriteResult.html */
 export interface BulkWriteResult {
-    ok: number;
+    /**
+     * Evaluates to `true` if the bulk operation correctly executes
+     */
+    ok: boolean;
+
+    /**
+     * The number of documents inserted, excluding upserted documents.
+     *
+     * @see {@link nUpserted} for the number of documents inserted through an upsert.
+     */
     nInserted: number;
-    nUpdated: number;
-    nUpserted: number;
+
+    /**
+     * The number of documents selected for update.
+     *
+     * If the update operation results in no change to the document,
+     * e.g. `$set` expression updates the value to the current value,
+     * {@link nMatched} can be greater than {@link nModified}.
+     */
+    nMatched: number;
+
+    /**
+     * The number of existing documents updated.
+     *
+     * If the update/replacement operation results in no change to the document,
+     * such as setting the value of the field to its current value,
+     * {@link nModified} can be less than {@link nMatched}
+     */
     nModified: number;
+
+    /**
+     * The number of documents inserted by an
+     * [upsert]{@link https://docs.mongodb.com/manual/reference/method/db.collection.update/#upsert-parameter}.
+     */
+    nUpserted: number;
+
+    /**
+     * The number of documents removed.
+     */
     nRemoved: number;
 
+    // Returns an array of all inserted ids
     getInsertedIds(): object[];
+    // Retrieve lastOp if available
     getLastOp(): object;
+    // Returns raw internal result
     getRawResponse(): object;
+
+    /**
+     * Returns the upserted id at the given index
+     * @param index the number of the upserted id to return, returns `undefined` if no result for passed in index
+     */
     getUpsertedIdAt(index: number): BulkWriteResultUpsertedIdObject;
+
+    // Returns an array of all upserted ids
     getUpsertedIds(): BulkWriteResultUpsertedIdObject[];
+    // Retrieve the write concern error if any
     getWriteConcernError(): WriteConcernError;
+
+    /**
+     * Returns a specific write error object
+     * @param index of the write error to return, returns `null` if there is no result for passed in index
+     */
     getWriteErrorAt(index: number): WriteError;
+
+    // Returns the number of write errors off the bulk operation
     getWriteErrorCount(): number;
+    // Retrieve all write errors
     getWriteErrors(): object[];
+    // Returns `true` if the bulk operation contains a write error
     hasWriteErrors(): boolean;
 }