When someone clicks a button I want my function to return `false` and the `keydown` function will be disabled.

Then, if I click this same button a second time, it will return `true` and the `keydown` function will be enabled.

I did like this but it only returns `false` and `keydown` function disabled. I also need to enable this `keydown` function by clicking this button.

How can I do this? 

```js
var controlsEnabled = true;
$(".keyboard-btn").on('click', function() {
  controlsEnabled = false;
});

$(document).keydown(function(e) {
  if (controlsEnabled) {
    if (e.keyCode == 38) {
      verticalSlideDown();
      console.log("pressed key for Down : " + e.keyCode);
    }

    if (e.keyCode == 40) {
      verticalSlideUp();
      console.log("pressed key for Up: " + e.keyCode);
    }

    if (e.keyCode === 13) {
      var div = $(".scroll-inner-container");
      console.log("pressed key for stop : " + e.keyCode);
      div.stop();
    }
  }
});
```

```html
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button class="keyboard-btn">click here</button>
```