JSFiddle - React, Tailwind, and code Playground

HTML

<span class="minus" onclick="minus('q_17601','кг')">-</span>

<input onchange="edit_q('q_17601','кг')" id="q_17601" size="6" class="quantity" name="quantity" value="1.0 кг" type="text">


<span class="plus" onclick="plus('q_17601','кг')">+</span>

<script type="text/javascript">

function edit_q(ID,base)
	{
var name_input = document.getElementById(ID);
		if (base=="кг" || base=="КГ"){
var g_numb=parseFloat(name_input.value);
g_numb=g_numb.toFixed(1);
			if (g_numb==NaN) {g_numb=0;}
name_input.value=g_numb+" "+base;
}
		else{
var g_numb=parseInt(name_input.value);
			if (g_numb==NaN) {g_numb=0;}
name_input.value=g_numb+" "+base;
		}
}


function plus(ID,base)
	{
var name_input = document.getElementById(ID);
		if (base=="кг" || base=="КГ"){
var g_numb=parseFloat(name_input.value)+0.1;
g_numb=g_numb.toFixed(1);
name_input.value=g_numb+" "+base;
}
		else{

name_input.value=parseInt(name_input.value)+1+" "+base;
		}
}
    
    function minus(ID,base)
	{
  var name_input = document.getElementById(ID);
if (base=="кг" || base=="КГ"){

  if (parseFloat(name_input.value)>0.1)
  {
var g_numb=parseFloat(name_input.value)-0.1;
g_numb=g_numb.toFixed(1);
name_input.value=g_numb+" "+base;
  }

}
		else{
  if (parseInt(name_input.value)>1)
  {
name_input.value=parseInt(name_input.value)-1+" "+base;
  }
		}
}
    
    
</script>