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.

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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>