Neatest (and fast) way to remove top lines from a textarea

Question

I have a webpage that displays last 1000 lines of a logfile then updates via AJAX every x seconds loading new content (if any) and appending to textare

Answer 1

You should be able to use a single split and then join after truncating the data, something like this:

// on data retrieved
var total = ((textarea.value 
              ? textarea.value + "\n" 
              : "") 
          + new_data).split("\n");

if (total.length > 10) 
    total = total.slice(total.length - 10);

textarea.value = total.join("\n");

Working example: http://jsfiddle.net/ArvQ7/ (cut to 10 lines for brevity)