What is function scope in JavaScript?

Function scope in JavaScript refers to the scope of variables and functions that are defined within a function. Variables and functions declared with the var keyword have function scope.

Variables declared inside a function are accessible only within that function and any nested functions. They are not accessible outside of the function in which they are defined. This means that variables declared within a function cannot be accessed before their declaration or outside of the function.

Example: Here, the variable x is declared inside the exampleFunction() function. It is accessible within that function and also within the innerFunction() nested inside it. However, x is not accessible outside of exampleFunction().

Javascript

function exampleFunction() {
  var x = 10; // Variable x has function scope
  console.log(x); // Output: 10

  function innerFunction() {
    console.log(x); // Output: 10
  }

  innerFunction();
}

exampleFunction();
// console.log(x); // Error: x is not defined

Output

10
10