Helpful Hyperlinks with JavaScript

There you are happily surfing a web site; you click a link and suddenly find yourself at another site being asked to download a file. What happened there? Annoying, isn’t it? There has to be a better way to indicate to your visitors where a link is going and to what type of file. So, to help solve this little annoyance, I’ve written a bit of JavaScript and CSS that adds pretty little icons after the links – depending on the file extension and location – to indicate to the user the type of document they’re about to load.

You can download the code here, and see an example.

The Brief

The main considerations when creating this functionality were:

simplicity – it must be easy to use

graceful degradation – in the case of CSS or/and JavaScript being disabled

minimal use of files – only one JavaScript and one CSS file

making it as plug-and-play as possible – so it can be quickly added to a site

limiting the overall amount of code

compatibility with all modern browsers, including IE6

Why the shift away from a CSS-only solution?

You can already do this in CSS, using attribute selectors. Here’s an example:

a[href$='.doc'] { 

  display: inline-block; 

  padding-left: 16px; 

  background: transparent url(images/icon_doc.gif) center right no-repeat; 

}

So why would you do it with a script, when most modern browsers will display the icons using just CSS?

The answer is simple: IE6. All decent browsers support CSS3 attribute selectors … except IE6. This bit of scripting with CSS makes IE6 play nicely; in fact, it even works in IE5.5.

Inspiration and Credit

Before we get started, I’d like to acknowledge the excellent – and free – Silk icons by Mark James at famfamfam, which we’ll be using in this article.

Silk icons

Also, credit where credit is due: this article was inspired by the piece Iconize Textlinks with CSS by Alexander Kaiser, which was in turn inspired by Ask the CSS Guy’s Showing Hyperlink Cues with CSS. In addition, I’ve used a couple of excellent functions written by SitePoint’s very own James Edwards, and a couple more taken from the Core JavaScript Library, written by Kevin Yank and Cameron Adams and immortalized in the SitePoint book, Simply JavaScript.

So how does it work?

Well, in a nutshell: we take all the links in the page, work out the file extension it links to, and then we add the appropriate icon after the link. Nice.

To make it all work, there are three files involved:

the HTML page containing the links, index.html

the CSS file containing the icon classes, iKonize.css

the JavaScript file that adds the CSS classes and icons to the links, iKonize.js

The Quick-Start Method

Now, if you’d like to sidestep the whys and wherefores, and just want to add it to your page, here’s the short version:

Add the links to the JavaScript and CSS files in the header of the page (change the file references to suit your site setup).
<link type="text/css" rel="stylesheet" href="iKonize.css"/> <script type="text/javascript" src="iKonize.js"></script>

Put your icons folder up on your site and make sure the url references are correct in the iKonize.css file.

Call the JavaScript function iKonize from a script tag included just before the closing body tag, like so:
<script type="text/javascript">iKonize();</script>

See – I told you it was simple to use!

For simplicity’s sake, I’ve opted to call the function from within the HTML after the DOM has loaded. There are other ways to achieve this using JavaScript, but they’re beyond the scope of this article.

The Full Explanation

Make yourself comfortable, we’re going to delve into the inner workings.

Configuration

In the spirit of keeping things simple, most of the setup is already done for you. You’ll only have to change the configuration if you need to alter the icons or file extensions. There are two places to make these changes: the JavaScript (iKonize.js), and the CSS file (iKonize.css).

Configure iKonize.js

At the top of the file you’ll see all the configuration variables: classPrefix, classExternal, and classIconLoc.

classPrefix is the prefix you want to give the individual CSS classes. Use this to prevent any conflicts with any existing CSS classes. The default is iKon_.

classExternal is the name of the CSS class you want to use to show a link to an external site.

externalIconLoc is the location of the image to use for the external icon.

Which links will receive an icon?

To define what type of file the link goes to, we’ll look at the file extension. The file types are split out into two groups: those that have unique icons, such as torrent files, and those that will share the same icon, but have different file extensions, such as Flash files (.fla and .swf).

Grouping file extensions that share the same icon saves you having hundreds of CSS classes and icons. To achieve this I have created two arrays.

The first array, IndividualClassArray, holds the file extensions of all the links with individual icons. The base of the CSS class name is the same as the file extension. That is, a text file is referenced with ‘txt‘ and the CSS class name is the classPrefix (set earlier) and ‘txt’ the base CSS class name, making a CSS class called ‘iKon_txt’ in this case.

IndividualClassArray = Array('txt', 'xls', 'css', 'torrent');

The second array, classArray, is actually a multidimensional array, but don’t let that put you off. Basically, it’s a group of individual arrays grouped according to the kind of icon we’d like to use. The first item in this array is IndividualClassArray (this array must always be the first array). The following arrays are similar to the previous array with one important difference: the first item in each of the arrays is the name of the CSS class that will be used, and the following items are the file extensions which need that class. In the following example the .swf and .fla file extensions will be associated with the ‘flash’ CSS class.

classArray = Array(  

IndividualClassArray,  

Array('flash', 'swf', 'fla')  

);

Note: File extensions exclude the dot, that is, xls not .xls.

For maximum portability, the actual CSS class name used will have a prefix such as ‘iKon_’, which we configured earlier – but in these arrays we always exclude the prefix. So a Flash CSS class is always referred to as ‘flash’ rather than ‘iKon_flash’.

External Links

To figure out whether a link is an external site, we need to know the host name of the current page.

For this we use:

url = parseURL(qualifyHREF(document.location.href)).hostname;

This takes the current document’s location and gets the domain name using the qualifyHREF function to make sure we have a fully qualified address and the parseURL function to get the host name. (Both of these functions were written by our resident JavaScript guru, Brothercake, and covered in his blog post). Later, when we add the classes for the external links, we’ll use this host name to work out whether the link is external to our site.

The Code That Actually Does the Work

Now we need to get all the links from the page using document.getElementsByTagName("a"), and determine the file extension of the link.

We do this by using the functions parseURL and qualifyHREF again.

First, take the href value of the a element:
linkHref = aElements[iv].href;

Next, parse the value to gain more information about the link:
oUrl = parseURL(qualifyHREF(linkHref));

Then get the extension for the link:
fileExt = oUrl.extension;

Then, we need to loop through these links and work out whether they need an icon. This is where it starts to become a little bit trickier. We need to loop through classArray and each of the arrays it contains. We do this by running a loop within a loop. Yes, that’s a loop, in a loop, in a loop! This hairy piece of code looks like this:

aElements = document.getElementsByTagName("a");  

iElements = aElements.length;  

  

for (iv = 0; iv < iElements; iv++) {  

  iLen = classArray.length;  

  for (ii = 0; ii < iLen; ii++) {  

      iArr = classArray[ii].length;  

        for (i = 0; i < iArr; i++) {  

            // Do we need to add an icon?  

          }  

     }  

}

Does this link require an icon?

To find out if we need to add an icon, we’ll compare the file extension of the link with each of the extensions listed in our arrays.

if (fileExt == classArray[ii][i]) {      

    if (ii === 0) {  

       linkClass = fileExt;  

    }  

    else {  

       linkClass = classArray[ii][0];  

    }  

    bFound = true;  



Now we know if the link needs an icon, and which class it needs. We'll add that class using the addClass function we've grabbed from the Core JavaScript Library.

if (bFound && linkClass !== '') {  

    addClass(aElements[iv], classPrefix + linkClass);  

}

Links to External Sites

Working out if the link is to an external site is just a case of comparing the URL host name we determined earlier with the URL we set in the configuration area.

if (oUrl.hostname.indexOf(url) == -1) { // not our url  

    bExternal = true;  

}

If it’s true, we’ll append a new image element in the anchor, add a source and ID, and then add an alt and title attribute for the image. We add the extra icon rather than just assigning a class to clearly show that this link goes to another site, as well as adding title and alt attributes to the icon.

if (bExternal) { //  an external link  

   img = document.createElement('img');  

   img.id = 'Newimg' + iv;  

   img.src = externalIconLoc;  

   img.alt = 'external site';  

   img.title = 'links to an external web site';  

   void (aElements[iv].appendChild(img));  

   oimg = document.getElementById("Newimg" + iv);  

   addClass(oimg, classExternal);  

}

The CSS Classes

Let’s move back to the CSS file now.

Here is our CSS class to add the icon to .doc files. Notice the class name is prefixed with ‘iKon_‘ and then the file extension ‘doc‘. This class basically puts a bit of padding in the top and bottom, and to the right of the link. It then adds a background image of the icon into that space.

.iKon_doc {  

  padding: 5px 20px 5px 0;  

  background: transparent url(icons/icon_doc.gif) no-repeat center right;  

}

For our external link icons, we’ll use a slightly different class structure. We add some padding top and bottom to make sure our icon is borderless.

.iKon_external{   

  padding: 5px 0 0 5px;  

  border: 0;  

}

If you changed the classPrefix variable, don’t forget to alter these class names to match.

Limitations

The link must have a file extension to have an icon assigned to the link (unless it’s an external site). The script also doesn’t recognize query string- based navigation links. If CSS is disabled, then only the external link icon will display and if JavaScript is disabled, then there are no visible changes to the page.

Conclusion

iKonize is a quick and easy way to add visually meaningful icons after links. The script works in IE5.5+ and can work independent of CSS3 attribute selectors. As you might expect, the script degrades well and is easily configured. I hope you find it useful!

Frequently Asked Questions about Hyperlinks in JavaScript

How can I create a hyperlink using JavaScript?

Creating a hyperlink using JavaScript involves manipulating the Document Object Model (DOM). You can create a new anchor element, set its href attribute, and then append it to the body of the document. Here’s a simple example:

var link = document.createElement('a');
link.href = "https://www.example.com";
link.textContent = "Go to Example.com";
document.body.appendChild(link);
In this code, we first create a new anchor element, then set its href attribute to the URL of the page we want to link to. We then set the text of the link, and finally append the link to the body of the document.

How can I change the target of a hyperlink using JavaScript?

The target of a hyperlink can be changed using the ‘target’ attribute. This attribute specifies where to open the linked document. It can be set to “_blank” to open the document in a new window or tab, “_self” to open the document in the same frame as it was clicked (this is default), “_parent” to open the document in the parent frame, or “_top” to open the document in the full body of the window. Here’s an example:

var link = document.createElement('a');
link.href = "https://www.example.com";
link.target = "_blank";
link.textContent = "Go to Example.com";
document.body.appendChild(link);
In this code, the target attribute is set to “_blank”, which means the link will open in a new window or tab.

How can I add a title to a hyperlink using JavaScript?

The title of a hyperlink can be added using the ‘title’ attribute. This attribute provides additional information about the link, such as the name of the linked document, and is often displayed as a tooltip when the mouse moves over the link. Here’s an example:

var link = document.createElement('a');
link.href = "https://www.example.com";
link.title = "Go to Example.com";
link.textContent = "Example";
document.body.appendChild(link);
In this code, the title attribute is set to “Go to Example.com”, which will be displayed as a tooltip when the mouse moves over the link.

How can I remove a hyperlink using JavaScript?

A hyperlink can be removed using the ‘removeChild’ method. This method removes a specified child node of the specified element. Here’s an example:

var link = document.getElementById('myLink');
link.parentNode.removeChild(link);
In this code, we first get the link element by its ID, then remove it from its parent node.

How can I change the text of a hyperlink using JavaScript?

The text of a hyperlink can be changed using the ‘textContent’ property. This property sets or returns the text content of the specified node, and all its descendants. Here’s an example:

var link = document.getElementById('myLink');
link.textContent = "New Link Text";
In this code, we first get the link element by its ID, then change its text content to “New Link Text”.

How can I style a hyperlink using JavaScript?

A hyperlink can be styled using the ‘style’ property. This property is used to add, change, or remove inline styles from an element. Here’s an example:

var link = document.getElementById('myLink');
link.style.color = "red";
link.style.fontSize = "20px";
In this code, we first get the link element by its ID, then change its color to red and its font size to 20 pixels.

How can I add an event listener to a hyperlink using JavaScript?

An event listener can be added to a hyperlink using the ‘addEventListener’ method. This method attaches an event handler to the specified element. Here’s an example:

var link = document.getElementById('myLink');
link.addEventListener('click', function() {
alert('You clicked the link!');
});
In this code, we first get the link element by its ID, then attach a click event listener to it. When the link is clicked, an alert box will be displayed.

How can I prevent a hyperlink from following the URL using JavaScript?

A hyperlink can be prevented from following the URL using the ‘preventDefault’ method. This method cancels the event if it is cancelable, meaning that the default action that belongs to the event will not occur. Here’s an example:

var link = document.getElementById('myLink');
link.addEventListener('click', function(event) {
event.preventDefault();
alert('You clicked the link, but it did not follow the URL.');
});
In this code, we first get the link element by its ID, then attach a click event listener to it. When the link is clicked, it will not follow the URL, and an alert box will be displayed instead.

How can I create a hyperlink that downloads a file using JavaScript?

A hyperlink that downloads a file can be created using the ‘download’ attribute. This attribute specifies that the target will be downloaded when a user clicks on the hyperlink. Here’s an example:

var link = document.createElement('a');
link.href = "https://www.example.com/myFile.pdf";
link.download = "myFile.pdf";
link.textContent = "Download My File";
document.body.appendChild(link);
In this code, we first create a new anchor element, then set its href attribute to the URL of the file we want to download. We then set the download attribute to the name of the file, and finally append the link to the body of the document.

How can I create a hyperlink that opens an email client using JavaScript?

A hyperlink that opens an email client can be created using the ‘mailto:’ protocol in the href attribute. This protocol opens the user’s email client with a new message, ready to be sent. Here’s an example:

var link = document.createElement('a');
link.href = "mailto:example@example.com";
link.textContent = "Email Me";
document.body.appendChild(link);
In this code, we first create a new anchor element, then set its href attribute to “mailto:example@example.com“. We then set the text of the link, and finally append the link to the body of the document.