day 11 js interview

Author: nilajcoder

JavaScript Interview/Day 11/demo.js

@@ -0,0 +1,171 @@
+/*
+
+Condition Check (if (num)):
+
+In JavaScript, the if statement checks whether num is truthy or falsy.
+A falsy value is a value that evaluates to false in a Boolean context. Common falsy values include 0, "" (empty string), null, undefined, and false.
+A truthy value is anything that is not falsy. For example, all non-zero numbers are truthy.
+Execution of Code Inside if:
+
+If num is truthy, the count variable is incremented by 1.
+Iterating Over the Array:
+
+When num = 0: if (0) evaluates to false, so count remains 0.
+When num = 1: if (1) evaluates to true, so count becomes 1.
+When num = 2: if (2) evaluates to true, so count becomes 2.
+When num = 3: if (3) evaluates to true, so count becomes 3.
+
+
+1. let count = 0;
+const nums = [0, 1, 2, 3];
+
+nums.forEach(num => {
+    if (num) {
+        count = count + 1;
+    }
+});
+
+console.log(count);//3
+
+
+
+2. console.log(typeof typeof(10))//string
+   console.log(typeof Array) //funtion
+   
+class abc {
+
+}
+console.log(typeof abc)//function
+
+
+console.log(typeof 10)//number
+console.log(typeof "10")//string
+console.log(typeof NaN)//number
+console.log(typeof Boolean)//function
+console.log(typeof undefined)//undefined
+console.log(typeof parseFloat)//function
+console.log(typeof Symbol)//function
+console.log(typeof BigInt)// function
+
+
+$full=5;
+console.log($full);//5
+
+ z=BigInt("9");
+ console.log(z);//9n
+
+let p=Symbol("hello");
+console.log(p);//Symbol(hello)
+
+
+3. function myFunc() {
+    "use strict"
+    xyz = 100;
+    console.log(xyz);
+}
+
+console.log(myFunc());//error
+
+
+function myFunc() {
+    
+    xyz = 100;
+    console.log(xyz);
+}
+
+console.log(myFunc())// 100 underdefined
+
+
+
+
+function myFunc() {
+    
+   var xyz = 100;
+    console.log(xyz);
+}
+
+console.log(myFunc())// 100 underdefined
+
+
+function myFunc() {
+      "use strict"
+    let xyz = 100;
+     console.log(xyz);
+ }
+ 
+ console.log(myFunc())// 100 underdefined
+
+
+
+ 4. 
+
+var: variable can be redeclared & updated. A global scope variable  before 2015 we used var
+
+
+but in 2015 in javascript has new features called ES6 and we use the following keyword
+
+let:variable can not be re-declared but can be updated. block scope variable.
+
+const: variable can not be re-declared or updated.A block scope variable.
+
+
+i)var xyz=1 + abc//1+ undefined =NAN
+ var abc=100
+console.log(xyz)//NAN
+
+
+
+ii)var xyz=1 + abc
+ abc=100
+console.log(xyz)//ERROR REF
+
+iii)let xyz=1 + abc
+ let abc=100
+console.log(xyz)//ERROR REF
+
+
+iv)const xyz=1 + abc
+ const  abc=100
+console.log(xyz)//ERROR REF
+
+
+5. 
+const data = {
+    name: "Nabil",
+}
+
+const abc = [1, 2, 3, 4]
+console.log(delete data);//false
+console.log(delete abc);//false
+
+Explanation of the delete Operator:
+The delete operator in JavaScript is used to remove properties from objects, not variables or constants.
+delete can only work on properties of objects that are configurable.
+Trying to use delete on a variable, function, or constant will not remove it but will typically result in false.
+
+
+
+6.  
+
+const a = [];
+const b = [];
+console.log(a == b);   // false
+console.log(a === b);  // false
+
+
+
+
+1. Arrays are Objects in JavaScript
+Both a and b are arrays, and arrays in JavaScript are objects.
+When comparing objects (or arrays), the comparison checks whether the two operands refer to the same memory location (i.e., the same instance in memory), not whether their contents are the same.
+2. a == b
+The == operator performs a loose equality check. It checks if a and b refer to the same object in memory.
+Here, a and b are two separate arrays (two separate instances in memory). Even though both are empty, they are distinct objects.
+Therefore, a == b evaluates to false.
+
+*/
+
+
+
+
+