Q21. What is a first class function?
In JavaScript, **first-class functions(first-class citizens)** mean that functions are treated like any other variable. That means: 1. You can assign a function to a vari...
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Q22. What is the difference between HTML and React event handling?
Below are some of the main differences between HTML and React event handling, 1. In HTML, the event name usually represents in _lowercase_ as a convention: ```html ``` Wh...
Q23. What is a first order function?
A first-order function is a function that doesn’t accept another function as an argument and doesn’t return a function as its return value. i.e, It's a regular function t...
Q24. What are synthetic events in React?
`SyntheticEvent` is a cross-browser wrapper around the browser's native event. Its API is same as the browser's native event, including `stopPropagation()` and `preventDe...
Q25. What is a higher order function?
A higher-order function is a function that either accepts another function as an argument, returns a function as its result, or both. This concept is a core part of JavaS...
Q26. What are inline conditional expressions?
You can use either _if statements_ or _ternary expressions_ which are available in JS(and JSX in React) to conditionally execute or render expressions. Apart from these a...
Q27. What is a unary function?
A unary function (also known as a **monadic** function) is a function that **accepts exactly one argument**. The term "unary" simply refers to the function's arity—the nu...
Q28. What is "key" prop and what is the benefit of using it in arrays of elements?
A `key` is a special attribute you **should** include when mapping over arrays to render data. _Key_ prop helps React identify which items have changed, are added, or are...
Q29. What is the currying function?
**Currying** is the process of transforming a function with **multiple arguments** into a sequence of **nested functions**, each accepting **only one argument** at a time...
Q30. What is Virtual DOM?
The _Virtual DOM_ (VDOM) is a lightweight, in-memory representation of _Real DOM_ used by libraries like React to optimize UI rendering. The representation of a UI is kep...