# Java Script: Smooth Scrolling Table of Contents

```javascript
document.querySelectorAll('nav#table-of-contents a').forEach(link => {
    link.addEventListener('click', (e) => {
        e.preventDefault();
        const targetId = link.getAttribute('href').substring(1);
        const targetSection = document.getElementById(targetId);
        if (targetSection) {
            targetSection.scrollIntoView({ behavior: 'smooth' });
        }
    });
});
```

This block of code is written in JavaScript and is designed to add a click event listener to a set of HTML links that are part of a table of contents in a web page. The purpose of this code is to create a smooth scrolling effect when a user clicks on one of the links in the table of contents, causing the page to scroll to the corresponding section of content. Let's break down the code step by step:

```javascript
document.querySelectorAll('nav#table-of-contents a'):
```

This line selects all the anchor (<a>) elements within a <nav> element with the id attribute set to "table-of-contents" in the HTML document. It returns a NodeList of these anchor elements.

```javascript
.forEach(link => { ... }):
```

This part of the code iterates through each anchor element selected in the previous step using the forEach method. For each anchor element (which is referred to as link inside the callback function), it performs the following actions.

```javascript
link.addEventListener('click', (e) => { ... }):
```

It adds a click event listener to each anchor element. When the anchor element is clicked, the code inside the callback function is executed.

```javascript
e.preventDefault();:
```

This line prevents the default behavior of the anchor link when it is clicked. In a typical scenario, clicking an anchor link would cause the browser to navigate to a new page or scroll to the linked section. By preventing this default behavior, the code takes control of the link's behavior.

```javascript
const targetId = link.getAttribute('href').substring(1);:
```

This line extracts the href attribute of the clicked anchor link. The href attribute typically contains the ID of the section to which the link should scroll. The .substring(1) part removes the leading '#' character from the href, leaving only the section's ID.

```javascript
const targetSection = document.getElementById(targetId);:
```

This line retrieves the HTML element with the specified ID (extracted from the href attribute). This element corresponds to the section of content that the link points to in the same document.

```javascript
if (targetSection) { ... }:
```

This conditional statement checks if a valid target section element was found. If the target section exists, the code inside the block will execute.

```javascript
targetSection.scrollIntoView({ behavior: 'smooth' });:
```

If a valid target section element is found, this line smoothly scrolls the viewport of the page to make the target section visible. The scrollIntoView method is used with the behavior option set to 'smooth' to create a smooth scrolling effect.

You can see this code snippet in action at this link:  [My Github](https://johnliter.github.io/Documentation-Page/)

In summary, this code enhances the user experience by enabling smooth scrolling when clicking on links within a table of contents that navigate to specific sections on the same web page. It does so by preventing the default link behavior, extracting the target section's ID from the link's href, finding the corresponding section element in the document, and smoothly scrolling the page to that section.