Can I add unit to a value inside css calc?

Question

I'm storing a value in the DOM right now using javascript:

document.documentElement.style.setProperty('--offset', offset+'px')

later on, I use it as a part of a calculation in an animaiton:

@keyframes upanim {
    from    {transform: translate3d(0,calc(var(--offset) - 100vh ),0);}
    to  {transform: translate3d(0,0,0);}
}

I now want to use that same value to calculate the speed of that animation, so that the speed is always the same number of pixels/second:

animation: upanim calc(var(--offset) * 0.002)s cubic-bezier(0, 0, 0.25, 1);

The problem is the 'px' and 's', I would like to add the unit inside the calculation instead and just store the value in the DOM. Is this possible?

Answer 1

To use a unitless css variable in a property that needs pixels, you need to multiply it by 1px

width: calc(var(--offset) * 1px);

So, I think that the best that you can get is setting the variable offset with no dimensions, and add this dimensions when used:

In the snippet, hover the body to see the elements moving at constant speed:

#t1 {
  --offset: 10;
}
#t2 {
  --offset: 20;
}
#t3 {
  --offset: 40;
}

.test {
  width: 100px;
  height: 40px;
  margin: 5px;
  background-color: antiquewhite;
  transform: translateX(calc(var(--offset) * 1vh));
}

body:hover .test {
  animation: move calc(var(--offset) * 0.2s) linear forwards;
  background-color: lightgreen;
}

@keyframes move {
    from  {transform: translateX(calc(var(--offset) * 1vh));}
      to  {transform: translateX(0);}
}

<div class="test" id="t1">ONE</div>
<div class="test" id="t2">TWO</div>
<div class="test" id="t3">THREE</div>