See Working Demo on jsFiddle: http://jsfiddle.net/qHL8Z/3/
$(function() {_x000D_
var timer = null,_x000D_
interval = 1000,_x000D_
value = 0;_x000D_
_x000D_
$("#start").click(function() {_x000D_
if (timer !== null) return;_x000D_
timer = setInterval(function() {_x000D_
$("#input").val(++value);_x000D_
}, interval);_x000D_
});_x000D_
_x000D_
$("#stop").click(function() {_x000D_
clearInterval(timer);_x000D_
timer = null_x000D_
});_x000D_
});
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
<input type="number" id="input" />_x000D_
<input id="stop" type="button" value="stop" />_x000D_
<input id="start" type="button" value="start" />
_x000D_