complete passing arguments by value and reference

Author: Evavic44

10-A_Closer_Look_At_Functions/README.md

@@ -14,7 +14,6 @@ function createBooking(flightNum, numPassengers, price) {
   console.log(booking);
   bookings.push(booking);
 }
-
 createBooking("LH123");
 ```
 
@@ -93,3 +92,45 @@ In a situation we want to skip a parameter, we can simply assign it `undefined`,
 ```js
 createBooking("LH123", undefined, 1000); // numPassengers = 1, price = 1000
 ```
+
+## How Passing Arguments Works (Values vs Reference)
+
+Passing a primitive type to a function is the same as creating a copy outside of the function, so the value is simply coppied. On the other hand when we pass an object to a function, it is just like copying the object, so whatever we change in the copy will also affect the original.
+
+For Example:
+
+```js
+const flight = "LH234";
+const eke = {
+  name: "Victor Eke",
+  passport: 24739479284,
+};
+
+const checkIn = function (flightNum, passenger) {
+  flightNum = "LH999";
+  passenger.name = `Mr. ${passenger.name}`;
+
+  if (passenger.passport === 24739479284) {
+    alert("Check in");
+  } else {
+    alert("Wrong passport");
+  }
+};
+
+checkIn(flight, eke);
+console.log(flight); // "LH234"
+console.log(eke); // Mr Victor Eke
+```
+
+Another example
+
+```js
+const newPassport = function (person) {
+  person.passport = Math.trunc(Math.random() * 10000000000);
+};
+
+newPassport(eke);
+checkIn(flight, eke);
+```
+
+In programming there are two terms used all the time when dealing with functions: `passing by value` and `passing by reference`. JavaScript does not have `passing by reference`, only `passing by value`.

10-A_Closer_Look_At_Functions/css/main.css

@@ -25,3 +25,31 @@ createBooking("LH123", 2, 800);
 createBooking("LH123", 2); // "LH123" 2 * 199 = 398
 createBooking("LH123", 5); // "LH123" 5 * 199 = 995
 createBooking("LH123", undefined, 1000); // 1(default value), 1000
+
+const flight = "LH234";
+const eke = {
+  name: "Victor Eke",
+  passport: 24739479284,
+};
+
+const checkIn = function (flightNum, passenger) {
+  flightNum = "LH999";
+  passenger.name = `Mr. ${passenger.name}`;
+
+  // if (passenger.passport === 24739479284) {
+  //   alert("Check in");
+  // } else {
+  //   alert("Wrong passport");
+  // }
+};
+
+checkIn(flight, eke);
+console.log(flight); // "LH234"
+console.log(eke); // Mr Victor Eke
+
+const newPassport = function (person) {
+  person.passport = Math.trunc(Math.random() * 10000000000);
+};
+
+newPassport(eke);
+checkIn(flight, eke);