I set the width of a textarea to 100%, but now I need to know how many characters can fit in one row.

I'm trying to write a javascript function to auto-grow/shrink a textarea. I'm trying to keep from using jquery since I just need this one function.

My logic is to rows = textarea.value.split('\n'), iterate through rows and count += rows[i].length/textarea.cols, then count += rows.length, and finally textarea.rows = count. The only problem is that count is too large because textarea.cols is too small.