array additions added.

Author: EhsanZB

02-Part II - ES2015 features/10-Array additions/notes.md

@@ -0,0 +1,87 @@
+## Array additions
+
+```js
+// ES5
+console.log(
+	[2,5,10,4,7,8,13,15].indexOf(10) //2
+)
+
+console.log(
+	[2,5,10,4,7,8,13,15].indexOf(10) > -1 // true
+)
+```
+
+* new ES6 Array methods:
+
+    * includes()
+    * find()   * when we need to use a CONDITION
+    * findIndex()
+    * .fill()
+    * .keys()
+    * .values()
+    * .enteries()
+
+#### .includes()
+
+```js
+console.log(
+	[2,5,10,4,7,8,13,15].includes(25) // false (there is no 25 in the array)
+)
+```
+
+#### .find()
+
+```js
+console.log(
+	[2,5,10,4,7,8,13,15].find(function(item){
+		// condition
+		// return  item === 7 // return the FIRST item that meets this condition
+		// return item > 8 // 10 (note that although 13 is greater than 8 but .find method starts from the beginning of the array and stops when meets the criteria)
+		return item % 2 !== 0 // 5
+	})
+)
+```
+* another example: the objective of this example is to find the user(s) who is admin.
+
+```js
+class User {
+	constructor(name, isAdmin) {
+		this.name = name;
+		this.isAdmin = isAdmin;
+	}
+}
+
+let users = [
+	new User('Massih', false),
+	new User('Ehsan', true),
+	new User('Alex', false)
+];
+
+// find the first user that is admin
+console.log(
+	users.find(user => user.isAdmin) // {name: "Ehsan", isAdmin: true}
+	users.find(user => user.isAdmin).name // Ehsan
+)
+```
+
+#### .enteries()
+
+> note that when using .enteries(), the items.indexOf() won't work
+
+```js
+// without .enteries()
+let items = ['item1', 'item2', 'item3'];
+for (let item of items) {
+	console.log(
+		`${item} with index of: ${items.indexOf(item)}`
+	)
+}
+
+// using .enteries()
+let items = ['item1', 'item2', 'item3'].entries();
+for (let item of items) {
+	console.log(
+		`${item}` // returns: index,item  for example (0,item1,1,item2,...)
+	)
+}
+```

README.md

@@ -54,7 +54,7 @@ Other useful references:
 07. Modules
 08. Promises
 09. String additions
-10. Array additions (_in progress_)
+10. Array additions
 11. Generators (_in progress_)
 12. Sets (_in progress_)
 13. Symbols (_in progress_)