You don't need a loop. Since you're only replacing one p
element, just call .replaceWith()
once with the full HTML string you're inserting.
DEMO: http://jsfiddle.net/Vfk4e/
$(function () {
$('.btnClick').click(function () {
var p = $('.data p');
var splitter = p.text().split(',');
var open = "<span class='dataseg'>";
var close = "</span>"
p.replaceWith(open + splitter.join(close + open) + close)
});
});