#sort-box {
  width: 100%;
}

#button-wrap {
  width: 100%;
  display: flex;

}

.sort-button {
  flex: 1;
  margin-right: 10px;
  width: 100%;
  display: block;
  border: none;
  background: #eee;
  outline: none;
  border-radius: none;
  height: 40px;
  resize: none;
  text-align: center;
  font-family: arial;
  font-size: 10px;
  line-height: 40px;
  text-transform: uppercase;
}

.active,
.sort-button:hover {
  background: #fde676;

}

#search {
  margin-right: 0px;
  text-align: left;
  padding: 0px 10px;
  flex: 1.5;
}

.sort-hold {
  width: 100%;
  background: #eee;
  margin-top: 10px;
  padding: 5px 0px;
}

.member {
  margin: 10px;
  width: calc(100% - 70px);
  height: 50px;
  line-height: 50px;
  padding: 0px 25px;
  text-transform: uppercase;
  font-family: arial;
  background: #fff;
  font-size: 10px;
  outline: 1px solid #ddd;
  outline-offset: -1px;
}
 

// Get the container element
var btnWrap = document.getElementById("button-wrap");

// Get all buttons with class="btn" inside the container
var btns = btnWrap.getElementsByClassName("sort-button");

// Loop through the buttons and add the active class to the current/clicked button
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";
  });
}


$("#everyone").click(sortEveryone);
function sortEveryone() { 
    console.log("button clicked!")
    $(".member").show();
}


for (var btn of btns) {
    $(btn).hasClass("everyone") == false ? btn.addEventListener("click", activeBtn) : "";
}

function activeBtn(e) {
    let targetId = e.target.id;
  let members = $(".member");
  
  for (var member of members) {
    $(member).hasClass(targetId) ? $(member).show() : $(member).hide();
  }
}

And I have add .everyone for everyone btn to make it more easier to handel.

Add class everyone to everyone btn and replace sort-hold member to class name instead of id

Fix #member to be .member

.member {
  margin: 10px;
  width: calc(100% - 70px);
  height: 50px;
  line-height: 50px;
  padding: 0px 25px;
  text-transform: uppercase;
  font-family: arial;
  background: #fff;
  font-size: 10px;
  outline: 1px solid #ddd;
  outline-offset: -1px;
}

// Get the container element
var btnWrap = document.getElementById("button-wrap");

// Get all buttons with class="btn" inside the container
var btns = btnWrap.getElementsByClassName("sort-button");

// Loop through the buttons and add the active class to the current/clicked button
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";
  });
}


$("#everyone").click(sortEveryone);
function sortEveryone() { 
    console.log("button clicked!")
    $(".member").show();
}

// add activeBtn function for all btns except .everyone
for (var btn of btns) {
    $(btn).hasClass("everyone") == false ? btn.addEventListener("click", activeBtn) : "";
}

function activeBtn(e) {
  let targetId = e.target.id;
  let members = $(".member"); 

  // if the member class has the same name as the btn id, show it else hide it
  for (var member of members) {
    $(member).hasClass(targetId) ? $(member).show() : $(member).hide();
  }
}

And I have added .everyone for everyone btn to make it more easier to handle.