scope this and arrow

Author: nainimaru

03_basics/2scopes.js

@@ -0,0 +1,62 @@
+
+//var c = 300
+let a = 300
+if (true) {
+    let a = 10
+    const b = 20                   //block scope
+    // console.log("INNER: ", a);
+    
+}
+
+             //global scope
+
+// console.log(a);
+// console.log(b);
+// console.log(c);
+
+
+//nested scope
+//child function can access the parent variable but not vice versa
+
+function one(){
+    const username= "Naini"
+
+    function two(){
+        const website= "youtube"
+        console.log(username);
+    }
+    // console.log(website);     connot be accessed
+
+    two()
+
+}
+
+//one()
+
+
+if (true) {
+    const username = "hitesh"
+    if (username === "hitesh") {
+        const website = " youtube"
+        // console.log(username + website);   will run
+    }
+    // console.log(website);    error
+}
+
+// console.log(username);       error
+
+
+//++++++++++++ interesting +++++++++++++
+
+console.log(addone(5))  //will run
+
+function addone(num){
+    return num + 1
+}
+
+
+
+addTwo(5)         //error if written before function declaration
+const addTwo = function(num){
+    return num + 2
+}

03_basics/3arrow.js

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+//this- refers to current context
+
+const user = {
+    username: "hitesh",
+    price: 999,
+
+    welcomeMessage: function() {
+        console.log(`${this.username} , welcome to website`);
+        console.log(this);
+    }
+
+}
+
+// user.welcomeMessage()
+// user.username = "sam"
+// user.welcomeMessage()
+
+// console.log(this);
+
+//global object in browser- windows
+
+// function chai(){
+//     let username = "hitesh"
+//     console.log(this.username);
+// }
+
+// chai()
+
+// const chai = function () {
+//     let username = "hitesh"
+//     console.log(this.username);
+// }
+
+const chai =  () => {
+    let username = "hitesh"
+    console.log(this);
+}
+
+// chai()
+
+// const addTwo = (num1, num2) => {
+//     return num1 + num2         //explicit return
+// }
+
+// const addTwo = (num1, num2) =>  num1 + num2    //implicit return
+
+// const addTwo = (num1, num2) => ( num1 + num2 )
+
+const addTwo = (num1, num2) => ({username: "hitesh"})
+
+
+console.log(addTwo(3, 4))  
+
+
+// const myArray = [2, 5, 3, 7, 8]
+
+// myArray.forEach()