Extracted getList to a function

index.js

@@ -67,10 +67,7 @@ client.on('message', message => {
 	}
 
 	else if (command === "list") {
-		fs.readFile('data.json', (err, data) => {
-			if (err) throw err;
-			data = JSON.parse(data);
-			const songs = data[message.author.id];
+		getList(message.author.id, songs => {
 			if (songs === undefined) {
 				message.reply("Vous n'avez pas encore ajouté de musiques");
 			} else {
@@ -140,4 +137,12 @@ function play(message, song_id) {
 	});
 }
 
+async function getList(user_id, callback) {
+	fs.readFile('data.json', (err, data) => {
+		if (err) throw err;
+		data = JSON.parse(data);
+		callback(data[user_id]);
+	});
+}
+
 client.login(config["discord-token"]);