Closures - Still unsure why the counter resets

Ok, let’s break this down.

This is the makeBirdCounter function from the video:

function makeBirdCounter() {
    var count = 0;
    return function () {
        count += 1;
        return count + ‘ birds’;
    }
}

makeBirdCounter is an example of an outer function. Let’s look at the line inside makeBirdCounter that says return. That function without a name is an inner function.

Remember: inner functions can access variables defined in outer functions.

When we call makeBirdCounter(), it’s going to return the inner function.

So, writing makeBirdCounter() will return this:

function() {
    count += 1;
    return count + ‘ birds’;
}

So, let’s call makeBirdCounter() and assign it to a variable called birdCounter:

var birdCounter = makeBirdCounter();

The birdCounter variable now points to the inner function that was on makeBirdCounter’s return line.

So, it’s like we directly assigned the inner function to the variable:

Var birdCounter = function() {
    count += 1;
    return count + ‘ birds’;
}

When we write birdCounter(), we are only calling the inner function.

Only this logic is ran each time we call birdCounter():

    count += 1;
    return count + ‘ birds’;

So, when we call birdCounter(), that line of code var count = 0 from the outer function is not read. That’s why the count doesn’t reset. Instead, our inner function increments the outer function's count variable.