Code To Get A Parent Spans Id Attribute

I am trying to pass a value of a <span> tag's id attribute to a
function. The following code is a stripped down version of what im
trying to do:

<span id="6">Name: <input name="name" type="text"><span
onClick="dosomething(???);" style="cursor:hand;">Do It!</span></span>

Where there is a <span> tag with an event handler, onClick, i want to
replace the ??? with something that will get the value of the parent
span tag, which in the above case would be &#396;'. i dont want to simply
enter 'dosomething(6)' as the innerHTML of the <span> tag will swap
between other <span> tags with different attribute values. if the code
could also be relative if possible too.