練習問題実装

app.js

@@ -1,8 +1,21 @@
 'use strict';
 const fs = require('fs');
 const fileName = './test.txt';
-for (let count = 0; count < 30; count++) {
-    fs.appendFile(fileName, 'おはようございます\n', 'utf8', () => {});
-    fs.appendFile(fileName, 'こんにちは\n', 'utf8', () => {});
-    fs.appendFile(fileName, 'こんばんは\n', 'utf8', () => {});
+
+function appendFilePromise(fileName, str) {
+  return new Promise((resolve) => {
+    fs.appendFile(fileName, str, 'utf8', () => resolve());
+  });
 }
+async function main() {
+  for (let count = 0; count < 500; count++) {
+    await appendFilePromise(fileName, 'あ');
+    await appendFilePromise(fileName, 'い');
+    await appendFilePromise(fileName, 'う');
+    await appendFilePromise(fileName, 'え');
+    await appendFilePromise(fileName, 'お');
+    await appendFilePromise(fileName, '\n');
+  }
+}
+
+main();

app2.js

@@ -0,0 +1,16 @@
+'use strict';
+const fs = require('fs');
+const fileName = './test.txt';
+
+function appendFilePromise(fileName, str){
+    return new Promise((resolve) =>{
+        fs.appendFile(fileName, str, 'utf8', () => resolve());
+    });
+}
+async function main() {
+    for (let count = 0; count < 30; count++) {
+        await appendFilePromise(fileName, 'おはようございます\n');
+        await appendFilePromise(fileName, 'こんにちは\n');
+        await appendFilePromise(fileName, 'こんばんは\n');
+    }
+}

app3.js

@@ -0,0 +1,19 @@
+'use strict';
+const fs = require('fs');
+const fileName = './test.txt';
+
+function appendFilePromise(fileName, str) {
+    return new Promise((resolve) => {
+        fs.appendFile(fileName, str, 'utf8', () => resolve());
+    });
+}
+
+for (let count = 0; count < 30; count++) {
+  appendFilePromise(fileName, 'おはようございます\n')
+    .then(() => {
+        return appendFilePromise(fileName, 'こんにちは\n');
+    })
+    .then(() => {
+        return appendFilePromise(fileName, 'こんばんは\n');
+    });
+}