The line const [count, setCount] = useState(0) is a React hook (useState) used to manage state in functional components.

Breakdown:

• count: This is the current state value (initialized to 0).
• setCount: This is the function used to update the count state.
• useState(0): React’s useState hook initializes the state with 0 (the initial value).

In short, it sets up a state variable count with an initial value of 0 and provides a way (setCount) to update that state.

What is const

const is a keyword in JavaScript used to declare a variable with a constant value. Once a variable is declared with const, its value cannot be reassigned, although if the value is an object or array, its properties or elements can still be modified.
Key Points:

Block-scoped: The const variable is limited to the block, statement, or expression in which it’s defined. Cannot be reassigned: You can’t reassign a new value to a const variable after it’s been declared. Must be initialized: A const variable must be assigned an initial value when declared.

Example:

const pi = 3.14;
pi = 3.1416; // This will throw an error because reassignment is not allowed.

However, with objects or arrays, the contents can be modified:

const person = { name: 'Alice' };
person.name = 'Bob'; // This is allowed (modifying a property).

In short, const is used to declare constants whose reference can’t change.