Explain the concept of closures in JavaScript.

Description : Closures are a fundamental concept in JavaScript. Explain how they work and provide an example.

Answer :

A closure in JavaScript is a function that has access to its own scope, the scope of the outer function, and the global scope. It allows a function to retain access to variables from its containing scope even after that function has finished executing. For example, a function defined inside another function can access the outer function's variables.

A closure is the combination of a function bundled together (enclosed) with references to its surrounding state (the lexical environment). When you create a closure, you gain access to an outer function’s scope from an inner function. Closures are automatically created every time a function is defined in JavaScript.

function foo() {
    let b = 1;
    function inner() {
        return b;
    }
    return inner;
}
let get_func_inner = foo();

console.log(get_func_inner());
console.log(get_func_inner());
console.log(get_func_inner());


<!DOCTYPE html>
<html>

<body>
    <h2>JavaScript Closures</h2>
    <button type="button" onclick="initaccount()">
          Click Me!
        </button>
    <p id="demo"></p>
    <script>
    function initaccount() {
        var balance = 1000;

        function currentbalance() {
            balance = balance - 100;
            alert(balance);
        }
        currentbalance();
    }
    </script>
</body>

</html>

A closure in JavaScript is a function that has access to its own scope, the scope of the outer function, and the global scope. It allows a function to retain access to variables from its containing scope even after that function has finished executing. For example, a function defined inside another function can access the outer function's variables.

A closure is the combination of a function bundled together (enclosed) with references to its surrounding state (the lexical environment). When you create a closure, you gain access to an outer function’s scope from an inner function. Closures are automatically created every time a function is defined in JavaScript.

function foo() {
    let b = 1;
    function inner() {
        return b;
    }
    return inner;
}
let get_func_inner = foo();

console.log(get_func_inner());
console.log(get_func_inner());
console.log(get_func_inner());


<!DOCTYPE html>
<html>

<body>
    <h2>JavaScript Closures</h2>
    <button type="button" onclick="initaccount()">
          Click Me!
        </button>
    <p id="demo"></p>
    <script>
    function initaccount() {
        var balance = 1000;

        function currentbalance() {
            balance = balance - 100;
            alert(balance);
        }
        currentbalance();
    }
    </script>
</body>

</html>

Category : Javascript

Created Date : 9/6/2024

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