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HTML 

              
                    <ul class="photo-list">
        <li class="photo scr-target anime__fadeIn">
            <img src="https://picsum.photos/350/350">
            <p>フェードイン</p>
        </li>
        <li class="photo scr-target anime__fadeInDown">
            <img src="https://picsum.photos/350/350">
            <p>フェードイン(上から)</p>
        </li>
        <li class="photo scr-target anime__fadeInUp">
            <img src="https://picsum.photos/350/350">
            <p>フェードイン(下から)</p>
        </li>
        <li class="photo scr-target anime__fadeInLeft">
            <img src="https://picsum.photos/350/350">
            <p>フェードイン(左から)</p>
        </li>
        <li class="photo scr-target anime__fadeInRight">
            <img src="https://picsum.photos/350/350">
            <p>フェードイン(右から)</p>
        </li>
        <li class="photo scr-target anime__zoomIn">
            <img src="https://picsum.photos/350/350">
            <p>ズームイン</p>
        </li>
        <li class="photo scr-target anime__zoomOut">
            <img src="https://picsum.photos/350/350">
            <p>ズームアウト</p>
        </li>
    </ul>

<!-- IE対応↓ -->
<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver"></script>
<!-- IE対応↑ -->
!

CSS 

              
                img {
    max-width: 100%;
}
.photo-list {
    padding: 500px 0;
    width: 90%;
    max-width: 1000px;
    margin: 0 auto;
}
.photo-list li {
    width: 300px;
    margin: 0 auto 100px;
}

/* アニメーション設定 */
.scr-target {
    /* アニメーション開始から終了までの所要時間 */
    -webkit-animation-duration: 1s;
    animation-duration: 1s;
    /* アニメーションが開始するまでの遅延時間 */
    -webkit-animation-delay: 0s;
    animation-delay: 0s;
    /* アニメーションのループ回数 - infiniteで無限ループ */
    -webkit-animation-iteration-count: 1;
    animation-iteration-count: 1;
    /* キーフレームアニメーションで指定したプロパティをアニメーション開始前、終了後に適用するかどうか */
    -webkit-animation-fill-mode: both;
    animation-fill-mode: both;
}
.scr-target[class*='fadeIn'],
.scr-target[class*='zoom'] {
    opacity: 0;
}

/* フェードイン */
@-webkit-keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}
@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}
.anime__fadeIn.is-active {
    -webkit-animation-name: fadeIn;
    animation-name: fadeIn;
}

/* フェードイン(上から) */
@-webkit-keyframes fadeInDown {
    from {
        opacity: 0;
        -webkit-transform: translate3d(0, -100%, 0);
        transform: translate3d(0, -100%, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
@keyframes fadeInDown {
    from {
        opacity: 0;
        -webkit-transform: translate3d(0, -100%, 0);
        transform: translate3d(0, -100%, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
.anime__fadeInDown.is-active {
    -webkit-animation-name: fadeInDown;
    animation-name: fadeInDown;
}

/* フェードイン(下から) */
@-webkit-keyframes fadeInUp {
    from {
        opacity: 0;
        -webkit-transform: translate3d(0, 100%, 0);
        transform: translate3d(0, 100%, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
@keyframes fadeInUp {
    from {
        opacity: 0;
        -webkit-transform: translate3d(0, 100%, 0);
        transform: translate3d(0, 100%, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
.anime__fadeInUp.is-active {
    -webkit-animation-name: fadeInUp;
    animation-name: fadeInUp;
}

/* フェードイン(左から) */
@-webkit-keyframes fadeInLeft {
    from {
        opacity: 0;
        -webkit-transform: translate3d(-100%, 0, 0);
        transform: translate3d(-100%, 0, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
@keyframes fadeInLeft {
    from {
        opacity: 0;
        -webkit-transform: translate3d(-100%, 0, 0);
        transform: translate3d(-100%, 0, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
.anime__fadeInLeft.is-active {
    -webkit-animation-name: fadeInLeft;
    animation-name: fadeInLeft;
}

/* フェードイン(右から) */
@-webkit-keyframes fadeInRight {
    from {
        opacity: 0;
        -webkit-transform: translate3d(100%, 0, 0);
        transform: translate3d(100%, 0, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
@keyframes fadeInRight {
    from {
        opacity: 0;
        -webkit-transform: translate3d(100%, 0, 0);
        transform: translate3d(100%, 0, 0);
    }

    to {
        opacity: 1;
        -webkit-transform: translate3d(0, 0, 0);
        transform: translate3d(0, 0, 0);
    }
}
.anime__fadeInRight.is-active {
    -webkit-animation-name: fadeInRight;
    animation-name: fadeInRight;
}

/* ズームイン */
@-webkit-keyframes zoomIn {
    from {
        opacity: 0;
        -webkit-transform: scale3d(0.3, 0.3, 0.3);
        transform: scale3d(0.3, 0.3, 0.3);
    }

    100% {
        opacity: 1;
    }
}
@keyframes zoomIn {
    from {
        opacity: 0;
        -webkit-transform: scale3d(0.3, 0.3, 0.3);
        transform: scale3d(0.3, 0.3, 0.3);
    }

    100% {
        opacity: 1;
    }
}
.anime__zoomIn.is-active {
    -webkit-animation-name: zoomIn;
    animation-name: zoomIn;
}

/* ズームアウト */
@-webkit-keyframes zoomOut {
    from {
        opacity: 0;
        -webkit-transform: scale3d(1.6, 1.6, 1.6);
        transform: scale3d(1.6, 1.6, 1.6);
    }
    100% {
        opacity: 1;
    }
}
@keyframes zoomOut {
    from {
        opacity: 0;
        -webkit-transform: scale3d(1.6, 1.6, 1.6);
        transform: scale3d(1.6, 1.6, 1.6);
    }
    100% {
        opacity: 1;
    }
}
.anime__zoomOut.is-active {
    -webkit-animation-name: zoomOut;
    animation-name: zoomOut;
}
!

JS 

              
                window.addEventListener("load", function() {
const target = document.querySelectorAll('.scr-target')
const targetArray = Array.prototype.slice.call(target);
const options = {
    root: null,
    rootMargin: '0px 0px',
    threshold: 0.5
};

const observer = new IntersectionObserver(callback, options)
targetArray.forEach(function (tgt) {
  observer.observe(tgt)
});

function callback(entries) {
  entries.forEach(function(entry, i) {
    const target = entry.target;
    if (entry.isIntersecting && !target.classList.contains('is-active')) {
        target.classList.add('is-active');
    }
  });
};
});
!
999px

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