添加eventlistener时未定义的数组元素

I am fairly new to javascript and I am trying to grab all the "td" elements in the DOM and add a click event to them. When the code finishes executing, i can see I have 37 elements in cells array, but when I click the element, I get "clicked td37 undefined" in my console statement no matter which element is clicked. I do not have a clue what is wrong and any help would be appreciated. I am fairly new to javascript and I am trying t