Prevent var from going negative

Question

I have a button with a var that start with a 0 and when you click a another button it increases to 1. But if you click the second button first, the var goes negative. The button is disabled at the beginning, but when it increases to 1 the button should be enabled.

When the page is loaded the button disabled, but when the var goes to 1 the button is still disabled. I tried: if(var == 0){document.getElementById("button1").disabled = true; return false;}

Answer 1

You can do something like in below snippet :

You can use any tag instead of input like div span h1 ... which ever you wish and style according to need .
This thing you will need to change will be change .value to .innerHTML everywhere like this(1 example) :
var units = document.getElementsByClassName("unitsMain")[0].innerHTML

function decreaseUnits() {
  var units = document.getElementsByClassName("unitsMain")[0].value
  if (units > 0) {
    units--;
    document.getElementsByClassName("unitsMain")[0].value = units;
  }
}

function increaseUnits() {
  var units = document.getElementsByClassName("unitsMain")[0].value
  units++;
  document.getElementsByClassName("unitsMain")[0].value = units;
}

<button class="decOrderUnits" onclick="decreaseUnits()"><i class="fa fa-minus"></i>-</button>
<input class="unitsMain" value="0" maxlength="3">
<button class="incOrderUnits" onclick="increaseUnits()"><i class="fa fa-plus"></i>+</button>