Arrow Functions in JS

Author: svivek2002

03_basics/03_arrow.js

@@ -0,0 +1,56 @@
+const user = {
+    username : "vivek",
+    price : 3999,
+    
+    welcomeMessage : function(){
+        console.log(`${this.username}, welcome to the website`);
+        // this keyword refers to the current context
+        console.log(this); // output the current object contents
+    }
+}
+// user.welcomeMessage()
+// user.username = "sam" // sam will be the username for this context
+// user.welcomeMessage()
+
+
+// *******    Important    ********
+// console.log(this); // current context empty {} as we are in node env. and there is no context in the global
+                   // but if you run this in browser, this (global object in browser) will be the window object
+
+// const chai = function(){
+//     let username = "vivek"
+// In normal functions, a this variable is created which references the  
+// objects that call them.
+//     console.log(this); 
+//     console.log(this.username); // undefined, as this will only work in objects and not in functions
+// }
+// chai()
+
+// arrow function
+const chai = () => {
+    let username = "vivek"
+    console.log(this); //  Since chai is an arrow function, it doesn't create its own this variable
+    console.log(this.username); // undefined, as this will only work in objects and not in functions
+}
+chai()
+
+// function print(){
+//     console.log(arguments); 
+// }
+// print(1,false,"hello") // [Arguments] { '0': 1, '1': false, '2': 'hello' }
+
+// const print = () =>{
+//     console.log(arguments); // there is no argument object in arrow function
+// }
+// print(1,false,"hello")
+
+const addTwo = (num1,num2) => { 
+    return num1 + num2 // return is mandatory if {} are used
+}
+console.log(addTwo(3,6))
+
+// implicit return 
+
+// const addTwoOneLiner = (num1,num2) => (num1 + num2) // parenthesis are important for return if you want to return objects, see below 
+// const addTwoOneLiner = (num1,num2) => ({username : "vivek"})
+console.log(addTwoOneLiner(5,5));