Top 10 Questions JS

1. What is JavaScript?
   • JavaScript is a high-level, interpreted scripting language that enables interactive web pages. It is part of the core trio of web technologies, alongside HTML and CSS.
2. What is the difference between == and === in JavaScript?
   • == is the loose equality operator that compares values for equality after performing type coercion if necessary. === is the strict equality operator that compares both the value and type, without performing type coercion.
3. What is a closure in JavaScript?
   • A closure is a function that has access to the parent scope’s variables, even after the parent function has closed.
4. How does JavaScript handle asynchronous operations?
   • JavaScript handles async operations through mechanisms like callbacks, promises, and async/await. The event loop, Web APIs (in the browser), and the task queue allow JS to perform non-blocking operations.
5. What is the difference between var, let, and const in JavaScript?
   • var is function-scoped and was the way to declare variables in ES5. let and const are block-scoped. While let allows variable reassignment, const does not.
6. What is hoisting in JavaScript?
   • Hoisting is JavaScript’s behavior of moving variable and function declarations to the top of their containing scope. However, only the declarations are hoisted; initializations are not.
7. How do you differentiate between null and undefined?
   • Both represent “no value” or “absence of a value.” However, undefined typically means a variable has been declared but not assigned a value. null is a value that represents no value or no object.
8. What is the prototype chain or prototype inheritance in JavaScript?
   • JavaScript objects have a link to another object called its prototype. When trying to access a property of an object, it first checks the object itself. If not found, it looks in the object’s prototype, then the prototype’s prototype, and so on, forming the prototype chain.
9. What are arrow functions, and how are they different from regular functions?
   • Introduced in ES6, arrow functions allow for a shorter syntax when writing functions. They also lexically bind the this value, meaning they don’t create their own this context, making them handy for certain scenarios.
10. What is the this keyword in JavaScript?

• this is a special keyword that refers to the context in which a function was invoked. Its value can be different based on how a function is called (e.g., as a method, as a constructor, with call/apply, or as a regular function).

Like with the React and JS questions, these answers are concise overviews. The depth of explanations and follow-ups can vary based on context and the expertise of the individual asking.