[j0hnik]

<style>
		table{
			border-collapse: collapse;
		}
		td{
		border: 1px solid gray;
		}
	</style>


	<table id="tab">
		<tr><td>34,5</td><td>3,5</td><td>36</td><td>23</td></tr>
		<tr><td>34,5</td><td>3,5</td><td>36</td><td>23</td></tr>
		<tr><td>34,5</td><td>3,5</td><td>36</td><td>23</td></tr>
	</table>
	<script>
		tab.onmouseup = e => {
			var tds = document.querySelectorAll('#tab td');
			var start = getSelection().anchorNode.parentNode;
			stop = getSelection().focusNode;
			stop = stop.tagName == 'TD'? stop:stop.parentNode;
			if([].indexOf.call(tds, start)>[].indexOf.call(tds, stop)) [start,stop] = [stop,start];
			if(stop.parentNode != start.parentNode) {
				console.error('МИМО! Можно выделять только одну строку!');
				return;
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			var arr = [start.textContent];
			while(stop !=start) {
				start = start.nextElementSibling;
				arr.push(stop.textContent);
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			console.log(arr);
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	</script>