If it's just for display purposes, you can render the text as upper or lower case in pure CSS, without any Javascript using the text-transform
property:
.myclass {
text-transform: lowercase;
}
See https://developer.mozilla.org/en/CSS/text-transform for more info.
However, note that this doesn't actually change the value to lower case; it just displays it that way. This means that if you examine the contents of the element (ie using Javascript), it will still be in its original format.