How To Wrap A Selected Text In A TextArea

I searched about this problem over Internet and found the same result many times, I found this example on stackoverflow [URL] but this example didn't work in my project; I am making a toolbar with buttons that insert HTML tags around the selected text in a <textarea>, this exemple didn't work because when the user click on a button the selected text won't be selected anymore because <textarea> loses focus and selected text will be unselected, I am targeting Firefox and compatible browsers so you don't need to give me the IE code; jQuery codes are accepted;