When I select a button to filter a set of divs (when it's active), I want to to be a certain color. This code works locally, but when I paste it into my website, multiple buttons start displaying as active. The rest of the code still works, but multiple buttons are colored at the same time. How do I fix this?

HTML

    <div class="filter_container" id="myBtnContainer">      
        <button class="btn active" onclick="filterSelection('all')" type="button"> Show all</button>
        <button class="btn cme_ce" onclick="filterSelection('cme_ce')" type="button"> CME/CE Session</button>
        <button class="btn industry" onclick="filterSelection('industry')" type="button"> Industry-Sponsored (non-CME/CE)</button>
        <button class="btn special" onclick="filterSelection('special')" type="button"> Special Event</button>
    </div> 

Javascript

    filterSelection("all")
function filterSelection(c) {
  var x, i;
  x = document.getElementsByClassName("filterDiv");
  if (c == "all") c = "";
  for (i = 0; i < x.length; i++) {
    w3RemoveClass(x[i], "show");
    if (x[i].className.indexOf(c) > -1) w3AddClass(x[i], "show");
  }
}

function w3AddClass(element, name) {
  var i, arr1, arr2;
  arr1 = element.className.split(" ");
  arr2 = name.split(" ");
  for (i = 0; i < arr2.length; i++) {
    if (arr1.indexOf(arr2[i]) == -1) {element.className += " " + arr2[i];}
  }
}

function w3RemoveClass(element, name) {
  var i, arr1, arr2;
  arr1 = element.className.split(" ");
  arr2 = name.split(" ");
  for (i = 0; i < arr2.length; i++) {
    while (arr1.indexOf(arr2[i]) > -1) {
      arr1.splice(arr1.indexOf(arr2[i]), 1);     
    }
  }
  element.className = arr1.join(" ");
}

var btnContainer = document.getElementById("myBtnContainer");
var btns = btnContainer.getElementsByClassName("btn");
for (var i = 0; i < btns.length; i++) {
  btns[i].addEventListener("click", function(){
    var current = document.getElementsByClassName("active");
    current[0].className = current[0].className.replace(" active", "");
    this.className += " active";
  });
}