As web developers, we are all familiar with the concept of URL or Uniform Resource Locator. It is the address of a particular webpage or file on the internet. But have you ever come across a URL with a hash or fragment identifier at the end? For example, https://www.example.com/#about. This additional part of the URL is known as a URL hash or fragment identifier and it can be incredibly useful for navigating within a webpage. In this article, we will learn how to parse URL hash/fragment identifier with JavaScript.
Firstly, let's understand what a URL hash or fragment identifier is. It is a string of characters that comes after the # symbol in a URL. It is used to specify a specific location within a webpage, usually an anchor tag. When a user clicks on a link with a hash in it, the browser automatically scrolls to the element on the webpage with the matching id. This is commonly used for smooth scrolling to a particular section on a long webpage or for creating a bookmarkable link.
Now let's see how we can access and manipulate the URL hash with JavaScript. To get the hash from a URL, we can use the location.hash property. For example, if we have the URL https://www.example.com/#about, then the value of location.hash will be "#about". We can also set the hash using the same property. So if we want to change the hash to "#contact", we can do so by setting location.hash = "#contact".
But what if we want to extract only the text after the hash symbol? For that, we can use the substring method to remove the # symbol from the hash string. So if we have the hash "#about", we can use location.hash.substring(1) to get "about". This is helpful when we want to use the hash value for some logic or to manipulate the page content.
Another important thing to keep in mind is that the hash value is automatically updated when a user clicks on a link with a hash in it. This means that we can use the onhashchange event to detect when the hash value has changed. This event is triggered whenever the hash changes, either by clicking on a link or by changing it programmatically. We can then use this event to perform some action, such as updating the page content or highlighting the corresponding navigation menu item.
Now let's look at a practical example of parsing URL hash with JavaScript. Say we have a webpage with three sections - Home, About, and Contact. Each section has a corresponding id - #home, #about, and #contact. We also have a navigation menu with links to these sections. When a user clicks on a menu item, we want the page to scroll to the corresponding section and highlight the menu item.
To achieve this, we can use the following code:
```
// get all the menu links
const links = document.querySelectorAll('.nav-menu a');
// loop through each link
links.forEach(link => {
// add event listener for click event
link.addEventListener('click', () => {
// remove active class from all links
links.forEach(link => link.classList.remove('active'));
// add active class to the clicked link
link.classList.add('active');
// get the hash value from the link
const hash = link.hash;
// scroll to the element with the matching id
document.querySelector(hash).scrollIntoView();
// set the hash in the URL
location.hash = hash;
});
});
// detect hash change
window.onhashchange = () => {
// remove active class from all links
links.forEach(link => link.classList.remove('active'));
// get the new hash value
const newHash = location.hash;
// add active class to the link with the matching hash
document.querySelector(`a[href="${newHash}"]`).classList.add('active');
}
```
In the above code, we first select all the menu links and add a click event listener to each of them. When a link is clicked, we first remove the active class from all the links and add it to the clicked link. Then we get the hash value from the link and scroll to the element with the matching id. Finally, we set the hash in the URL to maintain the scroll position.
We also detect the hash change using the onhashchange event and update the active class accordingly. This ensures that the correct menu item is always highlighted, even if the user changes the hash manually in the URL.
In conclusion, parsing URL hash/fragment identifier with JavaScript is a useful skill to have as a web developer. It allows us to create dynamic and user-friendly webpages without the need for complex code. So the next time you come across a URL with a hash, you'll know how to make the most of it. Happy coding!
