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 1)Given an number N and an array of size N-1 containing N-1 numbers between 1 to N. Find the number(between 1 to N), that is not present in the given array. let N = 5; let Arr = [1, 2, 4, 5]  sum=n*(n+1)/2 for(let i=0;i<arr.length;i++){ sum-=arr[i] } console.log(sum) 2)Input: pattern = "abba", s = "dog cat cat dog " Output: true function wordPattern(pattern, s) {     const words = s.split(' ');     if (pattern.length !== words.length) {         return false;     }          const charToWord = new Map();          for (let i = 0; i < pattern.length; i++) {         const char = pattern[i];         const word = words[i];                  if (charToWord.has(char)) {             if (charToWord.get(char) !== word) {               ...

 1)ES6 features: ES6 (ECMAScript 2015) introduced many new features and syntax improvements to JavaScript. Here are some notable ES6 features along with examples: 1. Arrow Functions: Arrow functions provide a more concise syntax for writing anonymous functions. javascript Copy code // ES5 function add(a, b) {   return a + b; } // ES6 const add = (a, b) => a + b; 2. Template Literals: Template literals allow embedding expressions inside strings using backticks (`). javascript Copy code // ES5 var message = "Hello, " + name + "!"; // ES6 let message = `Hello, ${name}!`; 3. Destructuring Assignment: Destructuring allows extracting values from objects or arrays and assigning them to variables. javascript Copy code // ES5 var person = { name: 'John', age: 30 }; var name = person.name; var age = person.age; // ES6 const { name, age } = { name: 'John', age: 30 }; 4. Spread Syntax: The spread syntax (...) allows expanding iterable objects (e.g., arrays) i...

 1)JWT token:           const jwt = require ( 'jsonwebtoken' ); A JWT token consists of three parts separated by dots ( . ): Header : Contains metadata about the type of token and the hashing algorithm used. Payload (Claims) : Contains the claims or statements about the subject of the token, such as user ID, roles, etc. Signature : Verifies that the sender of the JWT is who it says it is and ensures that the message wasn't changed along the way. It is header +payload +secret key. Methods: const newToken = jwt. sign (payload, secretKey, { expiresIn : '1h' }); Use verify() when you need to ensure the token's integrity and authenticity. Use decode() when you only need to extract information from the token and don't need to verify its signature. 2)Window ,this,global: In nodejs this and global refers to same global methods and varibales just that no dom related things that are in window. In nodejs no window. 3)a.getSum(); // Define the custom method getSu...

 1)call,apply,bind example? Ans: a. call Method: The call method is used to call a function with a given this value and arguments provided individually. Javascript code: function greet(name) {   console.log(`Hello, ${name}! I am ${this.role}.`); } const person = {   role: 'developer' }; greet.call(person, 'Alice'); // Output: Hello, Alice! I am developer. In this example, call invokes the greet function with person as the this value and passes 'Alice' as an argument. b. apply Method: The apply method is similar to call, but it accepts arguments as an array. Javascript code: function introduce(language1, language2) {   console.log(`I can code in ${language1} and ${language2}. I am ${this.name}.`); } const coder = {   name: 'Bob' }; introduce.apply(coder, ['JavaScript', 'Python']); // Output: I can code in JavaScript and Python. I am Bob. Here, apply is used to invoke introduce with coder as this and an array ['JavaScript', 'Pyt...