JavaScript function in href vs. onclick

bad:

<a id="myLink" href="javascript:MyFunction();">link text</a>

good:

<a id="myLink" href="#" onclick="MyFunction();">link text</a>

better:

<a id="myLink" href="#" onclick="MyFunction();return false;">link text</a>

even better 1:

<a id="myLink" title="Click to do something" href="#" onclick="MyFunction();return false;">link text</a>

even better 2:

<a id="myLink" title="Click to do something" href="PleaseEnableJavascript.html" onclick="MyFunction();return false;">link text</a>

Why better? because return false will prevent browser from following the link

best:

Use jQuery or other similar framework to attach onclick handler by element's ID.

$('#myLink').click(function(){ MyFunction(); return false; });

Putting the onclick within the href would offend those who believe strongly in separation of content from behavior/action. The argument is that your html content should remain focused solely on content, not on presentation or behavior.

The typical path these days is to use a javascript library (eg. jquery) and create an event handler using that library. It would look something like:

$('a').click( function(e) {e.preventDefault(); /*your_code_here;*/ return false; } );

In terms of javascript, one difference is that the this keyword in the onclick handler will refer to the DOM element whose onclick attribute it is (in this case the <a> element), whereas this in the href attribute will refer to the window object.

In terms of presentation, if an href attribute is absent from a link (i.e. <a onclick="[...]">) then, by default, browsers will display the text cursor (and not the often-desired pointer cursor) since it is treating the <a> as an anchor, and not a link.

In terms of behavior, when specifying an action by navigation via href, the browser will typically support opening that href in a separate window using either a shortcut or context menu. This is not possible when specifying an action only via onclick.

However, if you're asking what is the best way to get dynamic action from the click of a DOM object, then attaching an event using javascript separate from the content of the document is the best way to go. You could do this in a number of ways. A common way is to use a javascript library like jQuery to bind an event:

<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script><a id="link" href="http://example.com/action">link text</a><script type="text/javascript">    $('a#link').click(function(){ /* ... action ... */ })</script>