promises completed.

Author: EhsanZB

02-Part II - ES2015 features/08-Promises/notes.md

@@ -0,0 +1,64 @@
+## Promises
+
+* it is a `placeholder` (holding spot) for an `operation` that has `not` been taken place.
+* it's a `promise to do an action` - it hasn't done that yet! (it's `not the confirmation`! it just a promise!)
+* while the promise is a `placeholder for an action` which is `not completed `yet, so once it has been completed, then we can use `.then` to proceed to the following action.
+
+```js
+var promise = this.$http.get('/some/path');
+promise.then(function(data){
+    // doing something
+}).catch(function(err){
+    // error handling
+})
+```
+
+* note that we can also combine `.catch` with `.then` by passing it as the `second argument`:
+* although `.catch` is omitted but while it's located on the `second args of .then`, so it will `triggered as .catch`.
+
+```js
+promise.then(function(data){
+    // doing something
+}, function(err){
+    // error handling
+});
+```
+
+#### resolve and reject
+
+* resolve and reject `are functions` that we can `trigger` them based on the `result of the promise`.
+* note that `without` calling `resolve()` or r`eject()`, the `.then` part won't execute!
+* call reject() when an `error is thrown` (we need to be `explicit` about resolve and reject!)
+
+```js
+var timer = new Promise(function(resolve, reject) { // this function executes immediately (something like constructor!) - it's kinda bootstrap for our promise
+	console.log('initiating Promise!!!!');
+	setTimeout(function() {
+		console.log('timeout done!');
+		resolve();
+	}, 2000);
+});
+
+timer.then(function() { // it won't execute if we forgot to put resolve() inside the promise function (also called as Executor function)
+	console.log('doing something else after our timeout is done....');
+})
+```
+
+* a better approach to the previous example:
+
+```js
+var timer = function(length){
+	return new Promise(function(resolve, reject) {
+		console.log('initiating Promise!!!!');
+		setTimeout(function() {
+			console.log('timeout done!');
+			resolve();
+		}, length);
+	});
+};
+
+
+timer(3000).then(function() {
+	console.log('doing something else after our timeout is done....');
+});
+```

README.md

@@ -52,7 +52,7 @@ Other useful references:
 05. Object additions
 06. Classes
 07. Modules
-08. Promises (_in progress_)
+08. Promises
 09. String additions (_in progress_)
 10. Array additions (_in progress_)
 11. Generators (_in progress_)