Q921. What are shadowing and illegal shadowing?
Both **shadowing** and **illegal shadowing** refer to how variable names can "hide" or override others within nested scopes. **Shadowing** occurs when a variable declared...
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Q922. Why is it important to remove event listeners after use?
In JavaScript, you need to be mindful of removing event listeners to avoid memory leaks — especially in long-lived apps like single-page applications (SPAs) or when worki...
Q923. What is structuredClone and how is it used for deep copying objects?
In JavaScript, `structuredClone()` is a built-in method used to create a **deep copy** of a value. It safely clones nested objects, arrays, Maps, Sets, Dates, TypedArrays...
Q924. What is the difference between const and Object.freeze?
The main difference is that `const` applies to **variables** (bindings), while `Object.freeze()` applies to **values** (objects). 1. **`const`**: Prevents the reassignmen...
Q925. What is Promise.any and when should it be used?
`Promise.any()` is a Promise combinator method introduced in ES2021 that takes an iterable of promises and returns a single promise that fulfills as soon as any of the in...
Q926. What is BigInt and how is it different from Number?
`BigInt` is a built-in JavaScript object (introduced in ES2020) that provides a way to represent whole numbers larger than 2^53 - 1 (the largest number JavaScript can rel...
Q927. What are private class fields in JavaScript?
Private class fields (introduced in ES2022) are class properties that are only accessible within the class itself. They are prefixed with a hash symbol (`#`) and provide ...
Q928. What is the Array.prototype.at() method and why is it useful?
The `at()` method (introduced in ES2022) allows you to access array elements using both positive and negative indices. It provides a simpler and more intuitive way to acc...
Q929. What is top-level await in JavaScript modules?
Top-level await is a feature (introduced in ES2022) that allows you to use the `await` keyword at the top level of ES modules, outside of async functions. This enables mo...
Q930. What are WeakRef and FinalizationRegistry used for?
`WeakRef` and `FinalizationRegistry` are advanced features (introduced in ES2021) for managing memory and object lifecycles in JavaScript. They provide low-level control ...