🌟 Unraveling the Mysteries of Advanced JavaScript – A Deep Dive! 🚀🔍
JavaScript Questions and Answers
Question 6: What is a Promise in JavaScript and How Does it Work?
Answer:
A Promise in JavaScript is an object representing the eventual completion or failure of an asynchronous operation. It allows you to write asynchronous code in a more manageable way, avoiding the callback hell. A Promise is in one of these states: pending, fulfilled, or rejected.
Explanation:
A Promise starts in a pending state and eventually ends in either fulfilled (success) or rejected (failure). It provides .then(), .catch(), and .finally() methods to handle the outcome. Promises help in managing asynchronous operations like API calls, file reading, etc., by allowing you to chain operations and handle errors more gracefully.
Question 7: Explain the Concept of Hoisting in JavaScript.
Answer:
Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their containing scope during the compile phase. This means that variables and functions can be used before they are declared.
Explanation:
In JavaScript, var declarations and function declarations are hoisted to the top of their scope, not the assignments. However, let and const declarations are not hoisted in the same way. Understanding hoisting helps in avoiding reference errors and writing cleaner code.
Question 8: What is the Execution Context in JavaScript?
Answer:
The Execution Context is an abstract concept that holds information about the environment in which the current code is being executed. This includes the variable object (variables, function declarations, and arguments), the scope chain, and the value of this.
Explanation:
In JavaScript, code execution is done in execution contexts. There are two main types: global and functional. The global execution context is the base context, while a new execution context is created for each function call. Understanding execution contexts is crucial for understanding how closures, hoisting, and scope work in JavaScript.
Question 9: Describe Event Bubbling and Event Capturing in JavaScript.
Answer:
Event bubbling and capturing are two ways of event propagation in the HTML DOM API. In event bubbling, the event starts from the target element and bubbles up to the ancestors. In event capturing, the event starts from the topmost element and goes down to the target element.
Explanation:
JavaScript allows you to add event listeners to both the capture and bubble phases. By default, events are added in the bubbling phase. Understanding these concepts is crucial for complex event handling and dynamic content manipulation.
Question 10: What are Arrow Functions and How do they Differ from Regular Functions?
Answer:
Arrow functions are a concise syntax for writing function expressions in JavaScript. They allow shorter function syntax and do not have their own this, arguments, super, or new.target bindings.
Explanation:
Arrow functions are anonymous and change the way this binds in functions. In traditional functions, this refers to the object that called the function, which can change. In arrow functions, this is lexically bound, meaning it uses this from the code that contains the arrow function. This is particularly useful in callbacks and methods where you want to preserve the context of this.