Removed abstraction in asynchronous processing and rewrote it in a direct form

独自の抽象関数を使用せず、非同期処理を直接記述する形式に修正
- コールバックベースの処理をそのまま記述
- 非同期処理の流れが分かりやすくなるよう変更
- for文を使用せず、レコード追加を追加分そのまま記述

Author: sjabcdefin

03.asynchronous/sqlite_callback_error.js

@@ -12,58 +12,46 @@ const selectAllQuery = "SELECT * FROM movies";
 const deleteTableQuery = "DROP TABLE books";
 
 const titles = ["I Am a Cat", "I Am a Cat", "SANSHIRO"];
-let insertCount = 0;
 
-function main() {
-  createTable();
-}
-
-function createTable() {
-  db.run(createTableQuery, insertTitles);
-}
-
-function insertTitles() {
+db.run(createTableQuery, function () {
   console.log("Table created");
-  for (const title of titles) {
-    db.run(insertTitleQuery, [title], displayID);
-  }
-}
-
-function displayID(err) {
-  if (err) {
-    console.error(`Error occurred while inserting record: ${err.message}`);
-  } else {
-    console.log(`Record inserted successfully with ID: ${this.lastID}`);
-  }
-  insertCount++;
-  if (insertCount === titles.length) {
-    fetchAll();
-  }
-}
-
-function fetchAll() {
-  db.all(selectAllQuery, displayAll);
-}
-
-function displayAll(err, rows) {
-  if (err) {
-    console.error(`Error occurred while fetching records: ${err.message}`);
-  } else {
-    console.log("All records fetched successfully");
-    for (const row of rows) {
-      console.log(`id:${row.id}, title:${row.title}`);
+  db.run(insertTitleQuery, titles[0], function (err) {
+    if (err) {
+      console.error(`Error occurred while inserting record: ${err.message}`);
+    } else {
+      console.log(`Record inserted successfully with ID: ${this.lastID}`);
     }
-  }
-  deleteTable();
-}
-
-function deleteTable() {
-  db.run(deleteTableQuery, closeDB);
-}
-
-function closeDB() {
-  console.log("Table deleted");
-  db.close();
-}
-
-main();
+    db.run(insertTitleQuery, titles[1], function (err) {
+      if (err) {
+        console.error(`Error occurred while inserting record: ${err.message}`);
+      } else {
+        console.log(`Record inserted successfully with ID: ${this.lastID}`);
+      }
+      db.run(insertTitleQuery, titles[2], function (err) {
+        if (err) {
+          console.error(
+            `Error occurred while inserting record: ${err.message}`,
+          );
+        } else {
+          console.log(`Record inserted successfully with ID: ${this.lastID}`);
+        }
+        db.all(selectAllQuery, function (err, rows) {
+          if (err) {
+            console.error(
+              `Error occurred while fetching records: ${err.message}`,
+            );
+          } else {
+            console.log("All records fetched successfully");
+            for (const row of rows) {
+              console.log(`id:${row.id}, title:${row.title}`);
+            }
+          }
+          db.run(deleteTableQuery, function () {
+            console.log("Table deleted");
+            db.close();
+          });
+        });
+      });
+    });
+  });
+});

03.asynchronous/sqlite_callback_no_error.js

@@ -12,50 +12,26 @@ const selectAllQuery = "SELECT * FROM books";
 const deleteTableQuery = "DROP TABLE books";
 
 const titles = ["I Am a Cat", "KOKORO", "SANSHIRO"];
-let insertCount = 0;
 
-function main() {
-  createTable();
-}
-
-function createTable() {
-  db.run(createTableQuery, insertTitles);
-}
-
-function insertTitles() {
+db.run(createTableQuery, function () {
   console.log("Table created");
-  for (const title of titles) {
-    db.run(insertTitleQuery, [title], displayID);
-  }
-}
-
-function displayID() {
-  console.log(`Record inserted successfully with ID: ${this.lastID}`);
-  insertCount++;
-  if (insertCount === titles.length) {
-    fetchAll();
-  }
-}
-
-function fetchAll() {
-  db.all(selectAllQuery, displayAll);
-}
-
-function displayAll(err, rows) {
-  console.log("All records fetched successfully");
-  for (const row of rows) {
-    console.log(`id:${row.id}, title:${row.title}`);
-  }
-  deleteTable();
-}
-
-function deleteTable() {
-  db.run(deleteTableQuery, closeDB);
-}
-
-function closeDB() {
-  console.log("Table deleted");
-  db.close();
-}
-
-main();
+  db.run(insertTitleQuery, titles[0], function () {
+    console.log(`Record inserted successfully with ID: ${this.lastID}`);
+    db.run(insertTitleQuery, titles[1], function () {
+      console.log(`Record inserted successfully with ID: ${this.lastID}`);
+      db.run(insertTitleQuery, titles[2], function () {
+        console.log(`Record inserted successfully with ID: ${this.lastID}`);
+        db.all(selectAllQuery, function (err, rows) {
+          console.log("All records fetched successfully");
+          for (const row of rows) {
+            console.log(`id:${row.id}, title:${row.title}`);
+          }
+          db.run(deleteTableQuery, function () {
+            console.log("Table deleted");
+            db.close();
+          });
+        });
+      });
+    });
+  });
+});