1. I have a code that on button press runs autoscroll on a single table and when I use the autoscroll speed of 2500, the autoscroll works as it should to the end of the table, but when I change the speed to let’s say 11500 autoscroll works but not to the end of the table, 70% of the board just does autoscroll, so what should I need to change in the code to fix this error?
2. The same code and same table but I need an option to Scroll Page from Top to Bottom, then Back Up (and Repeat), please check the code of my autoscroll option and what should I change or insert to enable this option?

ini_set('MAX_EXECUTION_TIME', -1); define('SRT_STATE_SUBNUMBER', 0); define('SRT_STATE_TIME', 1); define('SRT_STATE_TEXT', 2); define('SRT_STATE_BLANK', 3); $lines = file("uploads/".$file_name); $subs = array(); $state = SRT_STATE_SUBNUMBER; $subNum = 0; $subText = ''; $subTime = ''; foreach($lines as $line) { switch($state) { case SRT_STATE_SUBNUMBER: $subNum = trim($line); $state = SRT_STATE_TIME; break; case SRT_STATE_TIME: $subTime = trim($line); $state = SRT_STATE_TEXT; break; case SRT_STATE_TEXT: if (trim($line) == '') { $sub = new stdClass; $sub->number = $subNum; list($sub->startTime, $sub->stopTime) = explode(' --> ', $subTime); $sub->text = $subText; $subText = ''; $state = SRT_STATE_SUBNUMBER; $subs[] = $sub; } else { $subText .= $line; } break; } } if ($state == SRT_STATE_TEXT) { // if file was missing the trailing newlines, we'll be in this // state here. Append the last read text and add the last sub. $sub->text = $subText; $subs[] = $sub; } ?> document.getElementById('table').style.display = 'block'; } function autoScroll(){ window.scrollBy(0,400) var objDiv = document.getElementById("table"); smooth_scroll_to(objDiv, objDiv.scrollHeight, 15900); } var smooth_scroll_to = function(element, target, duration) { target = Math.round(target); duration = Math.round(duration); if (duration < 0) { return Promise.reject("bad duration"); } if (duration === 0) { element.scrollTop = target; return Promise.resolve(); } var start_time = Date.now(); var end_time = start_time + duration; var start_top = element.scrollTop; var distance = target - start_top; var smooth_step = function(start, end, point) { if(point <= start) { return 0; } if(point >= end) { return 1; } var x = (point - start) / (end - start); return x*x*(3 - 2*x); } return new Promise(function(resolve, reject) { var previous_top = element.scrollTop; var scroll_frame = function() { if(element.scrollTop != previous_top) { reject("interrupted"); return; } var now = Date.now(); var point = smooth_step(start_time, end_time, now); var frameTop = Math.round(start_top + (distance * point)); element.scrollTop = frameTop; if(now >= end_time) { resolve(); return; } if(element.scrollTop === previous_top && element.scrollTop !== frameTop) { resolve(); return; } previous_top = element.scrollTop; setTimeout(scroll_frame, 0); } setTimeout(scroll_frame, 0); }); }