TCS Interview Questions and Answers

use strict is a directive in JavaScript that enforces stricter parsing and error handling.

• It enables modern JavaScript features and disallows certain syntax that could lead to errors.

• It must be placed at the beginning of a script or function.

• It helps in writing more secure and optimized code.

• Example: 'use strict'; var x = 010; // SyntaxError: Octal literals are not allowed in strict mode.'

API stands for Application Programming Interface. It is a set of protocols and tools for building software applications.

• API allows different software applications to communicate with each other

• API specifies how software components should interact

• API can be used to retrieve data from a server or database

• API can be used to integrate third-party services into an application

• API can be accessed using HTTP requests

• API documentation is important for understanding how to use it

There is only one type of array in JavaScript.

• JavaScript has only one type of array, which can hold any type of data.

• Arrays can be created using the array literal notation or the Array constructor.

• Arrays have a length property that returns the number of elements in the array.

• Arrays have various methods like push(), pop(), shift(), unshift(), splice(), etc.

Promise is an object representing the eventual completion or failure of an asynchronous operation.

• Promises are used to handle asynchronous operations in JavaScript

• They are a cleaner alternative to callbacks

• Promises have three states: pending, fulfilled, or rejected

• They can be chained using .then() and .catch() methods

• Example: new Promise((resolve, reject) => {...})

An anonymous function is a function without a name.

• Declared using function keyword without a name

• Can be assigned to a variable or passed as an argument

• Used for one-time use or as a callback function

• Example: const sum = function(a, b) { return a + b; }

Variables in JavaScript are defined using the 'var', 'let', or 'const' keywords.

• Use 'var' to declare a variable with function scope

• Use 'let' to declare a variable with block scope

• Use 'const' to declare a constant variable

• Variables can be assigned a value using the '=' operator

• Variables can be declared without assigning a value

• Variables can be declared and assigned in the same statement