If element translate 3d ... addClass

how can I write a script that does this?

If the div class "test" has the property translate3d (0px, 100px, 0px) add to this the "active" class else remove it.

I tried something like this but it's not right ...

setInterval(function(){
  if($('.test').css('transform') == 'translate3d(0px, 100px, 0px)') {
    $('.test').addClass('active');
  } else {
    $('.test').removeClass('active');
  }
}, 1);

You need to do it like below using regex match:-

$(document).ready(function(){
  $('.test').each(function(){
    console.log($(this).css('transform') == 'matrix(1, 0, 0, 1, 0, 100)');
    if($(this).css('transform') == "matrix(1, 0, 0, 1, 0, 100)"){
      $(this).addClass('active');
    } else {
      $(this).removeClass('active');
    }
  });
});

.active {
  color: red;
  font-size: 20px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="test" style="transform:translate3d(0px, 100px, 0px)">Hello</div><br/><br/>
<div class="test" style="transform:translate3d(10px, 10px, 100px)">Hello</div>

Note:- check the console.log() value and you will see it's a matrix

Reference Taken:- Get translate3d values of a div?

To check any element have transform property or not use below regex:-

/matrix(?:(3d)\(\d+(?:, \d+)*(?:, (\d+))(?:, (\d+))(?:, (\d+)), \d+\)|\(\d+(?:, \d+)*(?:, (\d+))(?:, (\d+))\))/)