Here, is the simple code where i'm trying to change the background color once I clicked on the button

```js
const colorBtn = document.querySelector('.colorBtn');
const bodyBcg = document.querySelector('body');
const colors = ['red', 'blue', 'yellow', 'green'];

colorBtn.addEventListener('click', changeColor);

    // const changeColor = () => {
    //     let random = Math.floor(Math.random() * colors.length);
    //     bodyBcg.style.background = colors[random];
    // };

function changeColor() {
    console.log('color change event');
    let random = Math.floor(Math.random() * colors.length);
    bodyBcg.style.background = colors[random];
}
```

```css
body {
    display: flex;
    min-height: 100vh;
    justify-content: center;
    align-items: center;
}

.colorBtn {
    padding: 0.25rem 0.5rem;
    border: 10px;
    background-color: gray;
    color: white;
    outline: none;
    cursor: pointer;
}
```

```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Hex Colors</title>
    <link rel="stylesheet" href="./main.css">
</head>
<body>
    <button type="button" class="colorBtn">Click here to change color</button>
    <script type="text/javascript" src="./script.js"></script>
</body>
</html>
```

But when we try with the Arrow Function named changeColor, it's not working:
Not able to understand the concept behind this.

```
const changeColor = () => {
let random = Math.floor(Math.random() * colors.length);
bodyBcg.style.background = colors[random];
};

```

As well, It works fine in the chrome browser, but when I tried to put debug point on the working changeColor function, 
It throws error: 

```
const colorBtn = document.querySelector('.colorBtn');
ReferenceError: document is not defined

```