Preloader doesn't disappear

Question

Hey I am trying to add preloader to my website but whatever I do it won't disappear or it stays above the page or something like that. I tried a lot of things but nothing works even though I tried to copy the same code that should work.

// Attempt 1
$(document).ready(function () {
  $(".loader").fadeOut("slow");
});

// Attempt 2
// setTimeout(function () {
//   $(".loader").fadeToggle();
// }, 3000);

.loader {
  background: #111;
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  position: fixed;
  z-index: 1;
}

.loader div {
  background: #fff;
  width: 16px;
  height: 32px;
  margin-left: 10px;
  animation: loader 1.2s infinite;
}

@keyframes loader {
  50% {
    height: 64px;
  }
}

.loader div:nth-child(1) {
  background: #ff9f1a;
  animation-delay: -0.4s;
}

.loader div:nth-child(2) {
  background: #fed330;
  animation-delay: -0.2s;
}

.loader div:nth-child(3) {
  background: #fffa65;
  animation-delay: 0s;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="loader">
  <div></div>
  <div></div>
  <div></div>
</div>

Answer 1

The slim version of the jQuery library doesn't have the fadeOut function.