New Folder 03 Basics / 01 Functions JS

Learned about functions, how to add 2 numbers in a function and get there result in return, what happens if we don't pass arguments in function call.

Author: aayushyadavz

03_Basics/01_functions.js

@@ -0,0 +1,67 @@
+// 1. Functions
+
+function myname() {
+    console.log("A");
+    console.log("y");
+    console.log("u");
+    console.log("s");
+    console.log("h");
+}
+myname() /* myName is reference of the function & () is execution of the function.
+
+---------------------------------------------------------------------------------------*/
+
+function addTwoNumbers(number1, number2) { // Here, number1 & number2 are Parameters.
+    console.log(number1 + number2);
+}
+// const result = addTwoNumbers(3, 4) // and Here, 3 & 4 are Arguments.
+/* Output : 7 
+But if we check the value in result variable, */
+// console.log(`Result : ${result}`); // Output : Result : undefined
+/* Printing console in function doesn't means it's returning the value. 
+
+To fix this,*/
+function addTwoNumbers2(number1, number2) {
+    // let result = number1 + number2
+    // return result
+    /* console.log("Ayush"); This will never be excecuted cause after return function
+    doesn't work. */
+}
+// const result = addTwoNumbers2(3, 4)
+// console.log(result); // Output: 7
+
+// One more method of doing the same,
+function addTwoNumbers3(number1, number2) {
+    return number1 + number2
+}
+const result = addTwoNumbers3(3, 10)
+console.log(result); /* Output: 13
+
+---------------------------------------------------------------------------------------*/
+
+// (i)
+function userLogin(username){
+    return `${username} just logged in.`
+}
+// console.log(userLogin("Ayush")); // Output: Ayush just logged in.
+
+// (ii)
+function userLogin2(username){
+    if (!username){ // (!username) states (username === undefined)
+        console.log("Please enter a username.");
+        return /* if "if" statement will be true then return will stop
+        code after the above console.log in this function. */
+    }
+    return `${username} just logged in.`
+}
+// console.log(userLogin2()); // Output: undefined
+// Output: Please enter a username.
+// console.log(userLogin2("Ayush"));
+// Output: Ayush just logged in. 
+
+// (iii)
+function userLogin3(username = "sam"){
+    return `${username} just logged in.`
+}
+console.log(userLogin3()); // Output: sam just logged in.
+console.log(userLogin3("Ayush")); // Output: Ayush just logged in.