Javascript closure

A closure in programming refers to the ability of a function to "remember" the variables in its lexical scope (the environment in which it was created). It's like the function "closes over" these variables, retaining access to them even after the outer function has finished executing.

In the example of the counter function:

var createCounter = function(n) {
    return function() {
        return n++;
    };
};

const counter = createCounter(10);
console.log(counter()); // Output: 10
console.log(counter()); // Output: 11
console.log(counter()); // Output: 12

Here, the createCounter function returns an inner function that has access to the n variable. When you call createCounter(10), it creates a closure around the variable n with an initial value of 10. The inner function is assigned to the variable counter.

Now, when you call counter(), it returns the current value of n (10 in the first call) and increments n for the next call. The closure allows the inner function to remember the state of n between calls.

Think of it like the inner function "closes over" the n variable, enclosing it within its scope and preserving its state. This is a powerful concept in JavaScript and is often used for creating functions with persistent state.