メモ：
jqueryは必要だったら追加

js (ヘッダーで外部読み込みしてもいい)

(function ($) {
  'use strict';


  $(function(){

    $(window).scroll(function (){
      var animTrigger = $('.anim');
      $(animTrigger).each(function(){
        var scroll = $(window).scrollTop(),
            elemTop = $(this).offset().top,
            windowHeight = $(window).height();

        if (scroll > elemTop - windowHeight + 200){
          $(this).addClass('is-animated');
        }
      });
    });
    $(window).trigger('scroll');

  });


  var $target = $('.js-anim'),
      $target2 = $('.js-anim2'),
      $target3 = $('.js-anim3');

  var anim = function() {
    if(($target).hasClass('is-animated')){
      $target.removeClass('is-animated');
      setTimeout(anim, 1000)
    } else {
      $target.addClass('is-animated');
      setTimeout(anim, 3000)
    }
  }
  anim();

  var anim2 = function() {
    if(($target2).hasClass('is-animated')){
      $target2.removeClass('is-animated');
      setTimeout(anim2, 1000)
    } else {
      $target2.addClass('is-animated');
      setTimeout(anim2, 4000)
    }
  }
  anim2();

  var anim3 = function() {
    if(($target3).hasClass('is-animated')){
      $target3.removeClass('is-animated');
      setTimeout(anim3, 3000)
    } else {
      $target3.addClass('is-animated');
      setTimeout(anim3, 3000)
    }
  }
  anim3();


})(jQuery);

css

  /*--------------------------------------------------
  エフェクト
  --------------------------------------------------*/
/* 上からフェードイン */
.slide-top {
  opacity: 0;
  transform: translate(0, -20px);
  transition: all 1s ease-out;
 }

/* 下からフェードイン */
.slide-bottom {
  opacity: 0;
  transform: translate(0, 20px);
  transition: all 1s ease-out;
 }

 /* 左からフェードイン */
.slide-left {
  opacity: 0;
  transform: translate(-20px, 0);
  transition: all 1s ease-out;
 }

/* 右からフェードイン */
.slide-right {
  opacity: 0;
  transform: translate(20px, 0);
  transition: all 1s ease-out;
 }


 /*--------------------------------------------------
  animetion
  --------------------------------------------------*/
.anim { opacity: 0; }
/* フェードイン */
.fadein.is-animated {
  animation: fadeIn 0.7s cubic-bezier(0.33, 1, 0.68, 1) 1 forwards;
}

@keyframes fadeIn {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}

/* スライドイン */
.slidein.is-animated {
  animation: slideIn 1s cubic-bezier(0.25, 1, 0.5, 1) 1 forwards;
}

@keyframes slideIn {
  0% {
    transform: translateX(180px);
    opacity: 0;
  }
  100% {
    transform: translateX(0);
  }
  40%,100% {
    opacity: 1;
  }
}

/* ズームイン */
.zoomin.is-animated {
  animation: zoomIn 0.8s cubic-bezier(0.25, 1, 0.5, 1) 1 forwards;
}

@keyframes zoomIn {
  0% {
    transform: scale(0.8);
    opacity: 0;
  }
  100% {
    opacity: 1;
    transform: scale(1);
  }
}

/* ぽよよん */
.poyoyon.is-animated {
  animation: poyoyon 0.5s cubic-bezier(0.12, 0, 0.39, 0) 1 forwards;
}

@keyframes poyoyon {
  0% {
    transform: translateX(140px);
    opacity: 0;
  }
  50% {
    transform: translateX(0);
  }
  65% {
    transform: translateX(30px);
  }
  100% {
    transform: translateX(0);
  }
  20%,100% {
    opacity: 1;
  }
}

/* ぽよよん2 */
.poyoyon2.is-animated {
  animation: poyoyon2 1s ease-in-out 1 forwards;
}

@keyframes poyoyon2 {
  0%  {
    transform: scale(1.0, 1.0) translate(0, 0);
  }
  15% {
    transform: scale(0.98, 0.9) translate(0, 5px);
  }
  30% {
    transform: scale(1.02, 1.0) translate(0, 8px);
  }
  50% {transform: scale(0.98, 1.05) translate(0, -8px);
  }
  70% {
    transform: scale(1.0, 0.9) translate(0, 5px);
  }
  100% {
    transform: scale(1.0, 1.0) translate(0, 0);
  }
  0%, 100% {
    opacity: 1;
  }
}

/* ぽよよん3 */
.poyoyon3 {
  animation: poyoyon3 2.5s infinite;
  opacity: 1;
}
@keyframes poyoyon3 {
  0%, 40% {
    transform: skew(0deg, 0deg);
  }
  5% {
    transform: skew(5deg, 5deg);
  }
  10% {
    transform: skew(-4deg, -4deg);
  }
  15% {
    transform: skew(3deg, 3deg);
  }
  20% {
    transform: skew(-2deg, -2deg);
  }
  25% {
    transform: skew(1deg, 1deg);
  }
  30% {
    transform: skew(-0.6deg, -0.6deg);
  }
  35% {
    transform: skew(0.3deg, 0.3deg);
  }
}


/* ポップアップ */
.popup.is-animated {
  animation: popup 0.6s cubic-bezier(0.22, 1, 0.36, 1) 1 forwards;
}

@keyframes popup {
  0% {
    transform: translateY(40px) scale(0.8);
    opacity: 0;
  }
  100% {
    transform: translateY(0) scale(1.0);
  }
  80%, 100% {
    opacity: 1;
  }
}

/* どくどく */
.poyopoyo {
  animation: poyopoyo 2s ease-out infinite;
  opacity: 1;
}
@keyframes poyopoyo {
  0%, 40%, 60%, 80% {
    transform: scale(1.0);
  }
  50%, 70% {
    transform: scale(0.95);
  }
}

/* ななめから出てくる */
.slide-skew.is-animated {
  animation: slide-skew 0.4s cubic-bezier(0.25, 1, 0.5, 1) 1 forwards;
}

@keyframes slide-skew {
  0% {
    transform: translate(180px,30px);
    opacity: 0;
  }
  100% {
    transform: translate(0,0);
  }
  20%,100% {
    opacity: 1;
  }
}


/* きらん */
.kiran {
  opacity: 1;
  overflow: hidden;
  position: relative;
  cursor: pointer;
}
.kiran::before {
  background-color: #fff;
  content: "";
  display: block;
  position: absolute;
  top: -100px;
  left: 0;
  width: 30px;
  height: 100%;
  opacity: 0;
  transition: cubic-bezier(0.32, 0, 0.67, 0);
}
.kiran:hover::before {
  animation: kiran 0.5s linear 1;
}

@keyframes kiran {
  0% {
    transform: scale(2) rotate(45deg);
    opacity: 0;
  }
  20% {
    transform: scale(20) rotate(45deg);
    opacity: 0.6;
  }
  40% {
    transform: scale(30) rotate(45deg);
    opacity: 0.4;
  }
  80% {
    transform: scale(45) rotate(45deg);
    opacity: 0.2;
  }
  100% {
    transform: scale(50) rotate(45deg);
    opacity: 0;
  }
}

/* 背景色が流れてくる */
.bg .bg-wrap {
  position: relative;
  display: inline-block;
  margin-top: 5px;
}
.bg.is-animated .bg-wrap::before {
  animation: bg 2.6s cubic-bezier(0.22, 1, 0.36, 1) forwards;
  background: linear-gradient(to right, #362ae0 0%,#3b79cc 50%,#42d3ed 100%);
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transform-origin: left center;
}
.bg .bg-wrap .inn {
  color: #fff;
  display: inline-block;
  font-size: 36px;
  font-weight: bold;
  padding: 5px 15px;
  position: relative;
  z-index: 1;
}

@keyframes bg {
  0% {
    opacity: 0;
    transform: scaleX(0) translateX(-5%);
  }
  30% {
    transform: scaleX(1) translateX(0);
  }
  100% {
    transform: scaleX(1) translateX(0);
  }
  30%, 100% {
    opacity: 1;
  }
}

/* 文字がぬるりと現れる */
.matrix .bg-wrap,
.matrix .bg-wrap .inn {
  display: block;
}

.matrix .bg-wrap {
  overflow: hidden;
  opacity: 0;
}

.matrix .bg-wrap + .bg-wrap {
  margin-top: 10px;
}

.matrix .bg-wrap .inn.large {
  font-size: 36px;
  font-weight: bold;
}
.matrix .bg-wrap .inn.small {
  font-size: 15px;
}

.matrix .bg-wrap .inn {
  opacity: 0;
  transform: matrix(1, 0, 0, 1, 0, 100);
  transition: 1.2s cubic-bezier(0.22, 1, 0.36, 1);
}

.matrix.is-animated .bg-wrap {
  opacity: 1;
}

.matrix.is-animated .bg-wrap .inn {
  opacity: 1;
  transform: matrix(1, 0, 0, 1, 0, 0);
}

/* 背景色が消えてから表示されるテキスト */
.mask-bg {
  color: transparent;
  display: inline-block;
  font-size: 36px;
  font-weight: bold;
  overflow: hidden;
  position: relative;
  transition: color 0ms 450ms;
}
.mask-bg::after {
  background: linear-gradient(to right, #362ae0 0%,#3b79cc 50%,#42d3ed 100%);
  bottom: 0;
  content: '';
  display: block;
  left: 0;
  position: absolute;
  right: 0;
  top: 0;
  transform: translate(0, 100%);
}

.mask-bg.is-animated {
  color: #362ae0;
}
.mask-bg.is-animated::after {
  animation: mask-bg 1.2s cubic-bezier(0.8, 0, 0.170, 1);
}

@keyframes mask-bg {
  0% {
    transform: translate(0, 101%)
  }
  40%, 60% {
    transform: translate(0, 0%)
  }
  100% {
    transform: translate(0, -100%)
  }
}


/* 線が伸びる */
.line {
  display: block;
  position: relative;
  margin-top: 20px;
}
.line::after {
  background: linear-gradient(to right, #362ae0 0%,#3b79cc 50%,#42d3ed 100%);
  content: '';
  display: block;
  height: 1px;
  width: 0;
  transform: translateX(-50%);
  transition: 1.2s cubic-bezier(0.22, 1, 0.36, 1);
  position: absolute;
  bottom: 0;
  left: 50%;
}
.line.is-animated::after {
  width: 100%;
}


/* フェードアップ */
.fadeup.is-animated {
  animation: fadeup 1s cubic-bezier(0.33, 1, 0.68, 1) 1 forwards;
}

@keyframes fadeup {
  0% {
    transform: translateY(30px);
    opacity: 0;
  }
  80% {
    opacity: 1;
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ボーダーが緩やかにつく */
.stroke {
  background: #f0f0f0;
  max-width: 400px;
  height: 250px;
  position: relative;
}

.stroke .border {
  content: "";
  position: absolute;
  opacity: 0;
}
.stroke .border.top,
.stroke .border.bottom {
  width: calc(100% - 20px);
}
.stroke .border.top {
  border-top: 3px solid #362ae0;
  right: 0;
  top: 0;
}
.stroke .border.bottom {
  border-bottom: 3px solid #362ae0;
  left: 0;
  bottom: 0;
}

.stroke .border.right,
.stroke .border.left {
  height: calc(100% - 20px);
}
.stroke .border.right {
  border-right: 3px solid #362ae0;
  right: 0;
  top: 0;
}
.stroke .border.left {
  border-left: 3px solid #362ae0;
  left: 0;
  bottom: 0;
}

.stroke.is-animated .border {
  opacity: 1;
}

.stroke.is-animated .border.top,
.stroke.is-animated .border.bottom {
  animation: stroke-width 1.8s cubic-bezier(0.22, 1, 0.36, 1);
}
.stroke.is-animated .border.right,
.stroke.is-animated .border.left {
  animation: stroke-height 1.8s cubic-bezier(0.22, 1, 0.36, 1);
}

@keyframes stroke-width {
  0% {
    width: 0;
    opacity: 1;
  }
  100% {
    width: calc(100% - 20px);
    opacity: 1;
  }
}

@keyframes stroke-height {
  0% {
    height: 0;
    opacity: 1;
  }
  100% {
    height: calc(100% - 20px);
    opacity: 1;
  }
}

/* 文字が滑らかに表示される */
.smooth {
  clip-path: inset(0 100% 0 0);
  display: inline-block;
  font-size: 36px;
  font-weight: bold;
  transition: 1.4s cubic-bezier(0.37, 0, 0.63, 1);
  transition-property: clip-path;
  line-height: 1;
  height: 40px;
  margin-top: 15px;
}
.smooth.is-animated {
  clip-path: inset(0);
}

/* ふわふわ */
.fuwafuwa {
  animation: fuwafuwa 3s infinite ease-in-out .8s alternate;
  background: url(../img/ico-apple.svg) no-repeat center center / 60px auto;
  display: inline-block;
  transition: 1.5s ease-in-out;
  width: 70px;
  height: 70px;
  margin-top: 15px;
}

@keyframes fuwafuwa {
  0% {
    transform:translate(0, 0) rotate(-7deg);
  }
  50% {
    transform:translate(0, -7px) rotate(0deg);
  }
  100% {
    transform:translate(0, 0) rotate(7deg);
  }
}

/* ゆったりスクロールボタン */

.scroll {
  display: inline-block;
  padding-top: 70px;
  position: relative;
}
.scroll::before {
  animation: scroll 3.5s infinite;
  border: solid #000;
  border-width: 0 0 1px 1px;
  content: "";
  display: inline-block;
  margin: auto;
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  transform: rotate(-45deg);
  width: 20px;
  height: 20px;
}
@keyframes scroll {
  0% {
    transform: rotate(-45deg) translate(0, 0);
  }
  80% {
    transform: rotate(-45deg) translate(-30px, 30px);
  }
  0%, 80%, 100% {
    opacity: 0;
  }
  40% {
    opacity: 1;
  }
}

/* くるくる回りながら出現 */
.kurukuru {
  background: linear-gradient(to right, #362ae0 0%,#3b79cc 50%,#42d3ed 100%);
  width: 50px;
  height: 50px;
  opacity: 0;
  padding-bottom: 40px;
}
.kurukuru.is-animated {
  animation: kurukuru 1.4s ease-out;
  opacity: 1;
}
@keyframes kurukuru {
  0%{
    transform: rotateY(0) translateY(40px);
    opacity: 0;
  }
  100%{
    transform: rotateY(360deg) translateY(0);
    opacity: 1;
  }
}

html

※sectionまるごとフェード表示
<section class="fadeup anim">
<h1>タイトル</h1>
<p>テキスト</p>
</section>

※h1タイトルのみフェード表示
<section>
<h1 class="fadeup anim">タイトル</h1>
<p>テキスト</p>
</section>