How to shorten javascript code?

Hi Dp members, does anybody know how I can shorten the code I have below? Maybe shorten it to only 1 function? I have know idea how to do this :S
Thanks for helping

<script>
function bold()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[b ]' + tmp + '[ /b]' + textarea.value.substring(textarea.selectionEnd);
}
function italic()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[i ]' + tmp + '[ /i]' + textarea.value.substring(textarea.selectionEnd);
}
function underline()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[u ]' + tmp + '[ /u]' + textarea.value.substring(textarea.selectionEnd);
}
function strike()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[s ]' + tmp + '[ /s]' + textarea.value.substring(textarea.selectionEnd);
}
function code()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[code ]' + tmp + '[ /code]' + textarea.value.substring(textarea.selectionEnd);
}
function quote()
{
var textarea = document.getElementById('detail');
var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
textarea.value = textarea.value.substring(0, textarea.selectionStart) + '[quote ]' + tmp + '[ /quote]' + textarea.value.substring(textarea.selectionEnd);
}
</script>


<a href="javascript:;" onclick="bold();">Bold</a>
<a href="javascript:;" onclick="italic();">Italic</a>
<a href="javascript:;" onclick="underline();">Underline</a>
<a href="javascript:;" onclick="strike();">Strike</a>
<a href="javascript:;" onclick="code();">Code</a>
<a href="javascript:;" onclick="quote();">Quote</a>


<form id="form1" name="form1" method="post" action="#">
<textarea name="detail" cols="50" rows="5" id="detail"></textarea>
<input name="p" type="hidden" value="2" /><br/><br/>
<input type="submit" name="Submit" value="Reply" /><br/><br/>
</form>

Code (markup):

 

<script>
var actions = 
{
	bold: '[b ]',
	italic: '[i ]',
	underline: '[u ]',
	strike: '[s ]',
	code: '[code ]',
	quote: '[quote ]',
};

function doit(action)
{
	if(actions[action])
	{
		var fin = actions[action].replace(/\[(\w+)\s/, '[ /$1');
		var textarea = document.getElementById('detail');
		var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
	textarea.value = textarea.value.substring(0, textarea.selectionStart) + actions[action] + tmp + fin + textarea.value.substring(textarea.selectionEnd);
	}
}

</script>


<a href="javascript:;" onclick="doit('bold');">Bold</a>
<a href="javascript:;" onclick="doit('italic');">Italic</a>
<a href="javascript:;" onclick="doit('underline');">Underline</a>
<a href="javascript:;" onclick="doit('strike');">Strike</a>
<a href="javascript:;" onclick="doit('code');">Code</a>
<a href="javascript:;" onclick="doit('quote');">Quote</a>


<form id="form1" name="form1" method="post" action="#">
<textarea name="detail" cols="50" rows="5" id="detail"></textarea>
<input name="p" type="hidden" value="2" /><br/><br/>
<input type="submit" name="Submit" value="Reply" /><br/><br/>
</form>

Code (markup):

 

Thanks again Kaimi
How could I edit the code so that [b ][ /b] and all the others don't have the space?

 

Don't worry, I've done it now

<script>
var actions = 
{
	bold: '[b]',
	italic: '[i]',
	underline: '[u]',
	strike: '[s]',
	code: '[code]',
	quote: '[quote]',
};

function doit(action)
{
	if(actions[action])
	{
		var fin = actions[action].replace(/\[(\w+)/, '[/$1');
		var textarea = document.getElementById('detail');
		var tmp = (textarea.value).substring(textarea.selectionStart, textarea.selectionEnd);
	textarea.value = textarea.value.substring(0, textarea.selectionStart) + actions[action] + tmp + fin + textarea.value.substring(textarea.selectionEnd);
	}
}

</script>


<a href="javascript:;" onclick="doit('bold');">Bold</a>
<a href="javascript:;" onclick="doit('italic');">Italic</a>
<a href="javascript:;" onclick="doit('underline');">Underline</a>
<a href="javascript:;" onclick="doit('strike');">Strike</a>
<a href="javascript:;" onclick="doit('code');">Code</a>
<a href="javascript:;" onclick="doit('quote');">Quote</a>


<form id="form1" name="form1" method="post" action="#">
<textarea name="detail" cols="50" rows="5" id="detail"></textarea>
<input name="p" type="hidden" value="2" /><br/><br/>
<input type="submit" name="Submit" value="Reply" /><br/><br/>
</form>

HTML: