How to select value/innerHTML of a certain within a certain ? Using Javascript only. No jQuery

<table><tr><td>foo1</td><td>bar1</td><td><input type="button" id="button1" onClick="get(this);"></td></tr><tr><td>foo2</td><td>bar2</td><td><input type="button" id="button2" onClick="get(this);"></td></tr></table>

Goal: To get buttons button1 and button2 to trigger the same function get() which should get the value of the first <td> in the same <tr> the button resides in. Which is, in this case: foo1 and foo2 respectively.

This is a rough outline of the function which should help understand what I'm trying to achieve-

function get(element){  alert(element.tr.first_td.innerHTML);}

I realize there was a jQuery solution to a similar problem. But I do not understand jQuery well enough to translate it back to JavaScript. If it is possible at all using JavaScript, please show me how.