Q41. How do you redeclare variables in a switch block without an error?
When you try to redeclare variables using `let` or `const` in multiple `case` clauses of a `switch` statement, you will get a SyntaxError. This happens because, in JavaSc...
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Q42. What are uncontrolled components?
The **Uncontrolled components** are form elements (like ``, ``, or ``) that **manage their own state internally** via the **DOM**, rather than through React state. You ca...
Q43. What is the Temporal Dead Zone?
The **Temporal Dead Zone (TDZ)** refers to the period between the start of a block and the point where a variable declared with `let` or `const` is initialized. During th...
Q44. What is the difference between createElement and cloneElement?
Both `React.createElement` and `React.cloneElement` are used to work with React elements, but they serve different purposes. #### **createElement:** Creates a new React e...
Q45. What is an IIFE (Immediately Invoked Function Expression)?
IIFE (Immediately Invoked Function Expression) is a JavaScript function that runs as soon as it is defined. The signature of it would be as below, ```javascript (function...
Q46. What is Lifting State Up in React?
When several components need to share the same changing data then it is recommended to _lift the shared state up_ to their closest common ancestor. That means if two chil...
Q47. How do you decode or encode a URL in JavaScript?
`encodeURI()` function is used to encode an URL. This function requires a URL string as a parameter and return that encoded string. `decodeURI()` function is used to deco...
Q48. What are Higher-Order Components?
A _higher-order component_ (_HOC_) is a function that takes a component and returns a new enhanced component with additional props, behavior, or data. It’s a design patte...
Q49. What is memoization?
Memoization is a functional programming technique which attempts to increase a function’s performance by caching its previously computed results. Each time a memoized fun...
Q50. What is children prop?
The `children` prop is a special prop in React used to pass elements between the opening and closing tags of a component. It is commonly used in layout and wrapper compon...