Scope of var

Scope essentially means where these variables are available for use. var declarations are globally scoped or function/locally scoped.

The scope is global when a var variable is declared outside a function. This means that any variable that is declared with var outside a function block is available for use in the whole window.

var is function scoped when it is declared within a function. This means that it is available and can be accessed only within that function.

To understand further, look at the example below.

var greeter = "hey hi";
    
function newFunction() {
    var hello = "hello";
}

Here, greeter is globally scoped because it exists outside a function while hello is function scoped. So we cannot access the variable hello outside of a function. So if we do this:

var tester = "hey hi";
    
function newFunction() {
        var hello = "hello";
}
console.log(hello); // error: hello is not defined

We'll get an error which is as a result of hello not being available outside the function.