<div class="parent" id="parent">
  <div class="children"></div>
  <div class="children"></div>
  <div class="children"></div>
  <div class="children"></div>
  <div class="children"></div>
  <div class="children"></div>
</div>
<button class="button" onclick="removeChildren()">
  Remove Children
</button>

.parent {
  display: flex;
  flex-wrap: wrap;
}

.children {
  background: #121212;
  height: 50px;
  width: 50px;
  margin: 15px;
}

.button {
  background: #121212;
  border: none;
  color: #fff;
  padding: 15px;
  display: block;
}

function removeChildren() {
  const parent = document.getElementById("parent");
  // parent.innerHTML = "";
  while (parent.hasChildNodes()) {
      parent.removeChild(parent.lastChild);
  }
}