What does href expression <a href="javascript:;"></a> do?

Question

An <a> element is invalid HTML unless it has either an href or name attribute.

If you want it to render correctly as a link (ie underlined, hand pointer, etc), then it will only do so if it has a href attribute.

Code like this is therefore sometimes used as a way of making a link, but without having to provide an actual URL in the href attribute. The developer obviously wanted the link itself not to do anything, and this was the easiest way he knew.

He probably has some javascript event code elsewhere which is triggered when the link is clicked, and that will be what he wants to actually happen, but he wants it to look like a normal <a> tag link.

Some developers use href='#' for the same purpose, but this causes the browser to jump to the top of the page, which may not be wanted. And he couldn't simply leave the href blank, because href='' is a link back to the current page (ie it causes a page refresh).

There are ways around these things. Using an empty bit of Javascript code in the href is one of them, and although it isn't the best solution, it does work.

basically instead of using the link to move pages (or anchors), using this method launches a javascript function(s)

<script>
function doSomething() {
  alert("hello")
}
</script>
<a href="javascript:doSomething();">click me</a>

clicking the link will fire the alert.

There are several mechanisms to avoid a link to reach its destination. The one from the question is not much intuitive.

A cleaner option is to use href="#no" where #no is a non-defined anchor in the document.

You can use a more semantic name such as #disable, or #action to increase readability.

Benefits of the approach:

• Avoids the "moving to the top" effect of the empty href="#"
• Avoids the use of javascript

Drawbacks:

• You must be sure the anchor name is not used in the document.
• The URL changes to include the (non-existing) anchor as fragment and a new browser history entry is created. This means that clicking the "back" button after clicking the link won't behave as expected.

Since the <a> element is not acting as a link, the best option in these cases is not using an <a> element but a <div> and provide the desired link-like style.

<a href="javascript:alert('Hello');"></a>

is just shorthand for:

<a href="" onclick="alert('Hello'); return false;"></a>

Refer to this:

<a href="Http://WWW.stackoverflow.com">Link to the website opened in different tab</a>
<a href="#MyDive">Link to the div in the page(look at the chaneged url)</a>
<a href="javascript:;">Nothing happens if there is no javaScript to render</a>

It is a way of making a link do absolutely nothing when clicked (unless Javascript events are bound to it).

It is a way of running Javascript instead of following a link:

<a href="Javascript: doStuff();">link</a>

When there isn't actually javascript to run (like your example) it does nothing.

It's used to write js codes inside of href instead of event listeners like onclick and avoiding # links in href to make a tags valid for HTML.

Interesting fact

I had a research on how to use javascript: inside of href attribute and got the result that I can write multiple lines in it!

<a href="
     javascript:
        a = 4;
        console.log(a++); 
        a += 2; 
        console.log(a++); 
        if(a < 6){ 
            console.log('a is lower than 6');
        } 
        else 
            console.log('a is greater than 6');
        function log(s){
            console.log(s);
        }
        log('function implementation working too');

">Click here</a>

• Tested in chrome Version 68.0.3440.106 (Official Build) (64-bit)

• Tested in Firefox Quantum 61.0.1 (64-bit)