update

async-await/0_callbacks.js

@@ -41,5 +41,14 @@ function entryPoint () {
         Time of completion: Sun Jun 30 2024
         I don't need execute_action's value
 
+    Callbacks are usually meant for asynchronous programming. When
+    we meet a function that accepts a callback, it is likely an
+    asynchronous function, such as time, such as
+    setTimeout(callback, delay).
+
+    The problem is that this makes the code harder to read
+    so modern JS is written using Promises and async/await
+    constructs.
+    
   */
   

async-await/1_promises.js

@@ -1,12 +1,17 @@
 // https://javascript.info/promise-basics
 
 /*
-    The function passed to Promise is called "executor".
-    and gets executed the moment the Promise is created.
+    The function passed to Promise is called "executor"
+    and gets executed synchronously the moment the Promise is created.
     When the Promise ends, the callback function should 
     either call the "resolve" or "reject" callbacks:
     resolve(value) — if the job is finished successfully, with result value.
     reject(error) — if an error has occurred, error is the error object.
+
+    A Promise can be in one of these three states:
+    - Pending (the operation is being processed)
+    - Fullfilled (the operation has completed successfully)
+    - Rejected 
 */
 const promise = new Promise(function (resolve, reject) {
     setTimeout(() => resolve('done'), 500);

async-await/event-loop.txt

@@ -0,0 +1,3 @@
+JavaScript is single-threaded (but note that NodeJS is not entirely single-threaded, as it internally mantains a thread pool), but it can still take advantage of asynchronous programming.
+
+The Event Loop, which is a JavaScript construct that completes a new task while waiting for another