Javascript Questions

The ‘this’ keyword refers to the object that is currently executing the code. It is used to access properties and methods of an object.

Set object is used to perform set operations.

Variables are moved to the top of their scope before code execution

• Date;
• Math;
• String;
• Array.

Higher Order Functions are functions that take other functions as arguments or return other functions.

The strict mode is a way to make JavaScript more strict. It is used to prevent some common mistakes that can lead to JavaScript errors.

Implicit type coercion is a process in which a variable is automatically converted to a different type when it is assigned a value.

JavaScript is a dynamically typed language.

You can use try/catch blocks to handle exceptions

The try statement allows you to define a block of code to be tested for errors while it is being executed.

The catch statement allows you to define a block of code to be executed if an error occurs in the try block.

var

It's hoisted (always declared at top of the scope, global if none) and has function scope.

let

It has a block scope and is not redeclarable.

const

It has block scope, it's not reassignable and it's not redeclarable.

Memoization is an optimization technique used primarily to speed up programs that make repeated calculations.

Recursion is a technique in which a function calls itself. It is used to solve problems that can be solved by breaking down the problem into simpler sub-problems.

The unshift method is used to add an element to the beginning of an array.

Scope is the visibility of variables and functions.

Scope chain is the order in which the variables and functions are searched for a variable or function.

• Rest Parameter collects all remaining elements of an array or object into an array.
• Spread Operator expands collected elements such as arrays or objects into single elements.
• The spread syntax only does a shallow copy one level deep.
• Only the last parameter can be a rest parameter.

A Promise represents something that is eventually fulfilled. A Promise can be rejected, resolved or pending based on the operation outcome.

Object destructuring is a JavaScript feature that allows you to extract data from objects into distinct variables.

• Light Weight Scripting language
• Dynamic Typing
• Object-oriented programming support
• Functional Style
• Platform Independent
• Prototype-based
• Interpreted Language
• Async Processing
• Big Community
• Client-Side Validation

• Client-Side Security - Since JavaScript code is executed on the client-side, bugs and oversights can sometimes be exploited for malicious purposes. Because of this, some people choose to disable JavaScript entirely.
• Browser Support - While server-side scripts always produce the same output, different browsers sometimes interpret JavaScript code differently. These days the differences are minimal, and you shouldn't have to worry about it as long as you test your script in all major browsers.

Math object is used to perform mathematical operations.

Date object is used to perform date operations.

Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution

Functions are fully hoisted, but varibles are semi-hoisted.