- Answer: JavaScript is a versatile and widely-used programming language primarily used for front-end web development. It allows developers to add interactivity and dynamic behavior to web pages.
2. What is the difference between null and undefined?
- Answer: null represents the intentional absence of any value. undefined is the default value of a variable that has been declared but not assigned a value.
3. Explain the concept of closures in JavaScript.
- Answer: A closure is a function that retains access to variables from its outer (enclosing) function even after the outer function has finished executing. This allows the inner function to continue referencing those variables.
4. What is the purpose of the this keyword in JavaScript?
- Answer: The this keyword refers to the context in which a function is executed. It can be affected by how the function is called, and it helps to access properties and methods of an object.
5. How does prototypal inheritance work in JavaScript?
- Answer: Objects in JavaScript can inherit properties and methods from other objects through their prototype chain. If a property or method is not found in the current object, JavaScript looks up the prototype chain to find it.
6. Explain the event delegation pattern in JavaScript.
- Answer: Event delegation involves attaching an event listener to a common ancestor of multiple elements, instead of attaching listeners to each individual element. This is useful for improving performance and handling dynamic content.
7. What are the different data types in JavaScript?
- Answer: JavaScript has primitive data types: string, number, boolean, null, undefined, and symbol (ES6). It also has a non-primitive data type: object.
8. What is asynchronous programming in JavaScript?
- Answer: Asynchronous programming allows tasks to run in the background while the main program continues to execute. This is crucial for handling tasks like network requests, timers, and user input without blocking the main thread.
9. What is the purpose of the bind, call, and apply methods?
- Answer: These methods are used to control the value of the this keyword when calling a function. bind creates a new function with a fixed this value. call and apply immediately invoke the function with the provided this value and arguments.
10. How can you handle errors in JavaScript?
- Answer: JavaScript provides the try...catch statement for handling runtime errors. Code inside the try block is executed, and if an exception is thrown, it's caught and processed in the catch block.
Remember that interview questions may vary in complexity, and understanding the underlying concepts is key to providing strong answers. These answers provide a general overview; feel free to elaborate further during interviews.
