如何延迟 html/css 加载直到项目在视口中

Question

我在图表上有一个动画，但我希望 CSS 动画在进入用户视口后加载。目前它在页面加载时加载，但这意味着一旦用户滚动到该部分，动画就已经发生了。

下面可以看到HTML & CSS:

.chart[data-percent='100'] .outer {
  stroke-dashoffset: 0;
  -webkit-animation: show100 2s;
  animation: show100 2s;
}

.chart[data-percent='96'] .outer {
  stroke-dashoffset: 22;
  -webkit-animation: show96 2s;
  animation: show96 2s;
}

.chart[data-percent='77'] .outer {
  stroke-dashoffset: 123;
  -webkit-animation: show75 2s;
  animation: show75 2s;
}

.chart[data-percent='75'] .outer {
  stroke-dashoffset: 133;
  -webkit-animation: show75 2s;
  animation: show75 2s;
}

.chart[data-percent='52'] .outer {
  stroke-dashoffset: 257;
  -webkit-animation: show52 2s;
  animation: show52 2s;
}

.chart[data-percent='50'] .outer {
  stroke-dashoffset: 267;
  -webkit-animation: show50 2s;
  animation: show50 2s;
}

.chart[data-percent='25'] .outer {
  stroke-dashoffset: 401;
  -webkit-animation: show25 2s;
  animation: show25 2s;
}

@-webkit-keyframes show100 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 0;
  }
}

@keyframes show96 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 22;
  }
}

@keyframes show75 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 124;
  }
}

@-webkit-keyframes show52 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 257;
  }
}

@-webkit-keyframes show50 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 267;
  }
}

@keyframes show25 {
  from {
    stroke-dashoffset: 537;
  }
  to {
    stroke-dashoffset: 401;
  }
}

<div class="row stat-wheel">
  <div class="col-sm-4">
    <p class="stat-figure">52%</p>
    <figure class="chart" data-percent="52">
      <svg width="200" height="200">
        <circle class="outer" cx="95" cy="95" r="85" transform="rotate(-90, 95, 95)"/>
      </svg>
    </figure>
    <p class="white center">increase in sales generated through campaigns</p>
  </div>
  <div class="col-sm-4">
    <p class="stat-figure">77%</p>
    <figure class="chart" data-percent="77">
      <svg width="200" height="200">
        <circle class="outer" cx="95" cy="95" r="85" transform="rotate(-90, 95, 95)"/>
      </svg>
    </figure>
    <p class="white center">return on investment in the first 2 months</p>
  </div>
  <div class="col-sm-4">
    <p class="stat-figure">96%</p>
    <figure class="chart" data-percent="96">
      <svg width="200" height="200">
        <circle class="outer" cx="95" cy="95" r="85" transform="rotate(-90, 95, 95)"/>
      </svg>
    </figure>
    <p class="white center">increase in the quality of sales leads generated</p>
  </div>
</div>

Answer 1

您可以查看 intersection observer api，它会告诉您元素何时在您的视口中可见。你可以听它然后开始你的动画。

Answer 2

一种非常干净的方法是使用 vanilla JS。 Link with explanation

// (c) 2017 Chris Ferdinandi
var isInViewport = function (elem) {
    var distance = elem.getBoundingClientRect();
    return (
        distance.top >= 0 &&
        distance.left >= 0 &&
        distance.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&
        distance.right <= (window.innerWidth || document.documentElement.clientWidth)
    );
};

var findMe = document.querySelector('.row stat-wheel');

window.addEventListener('scroll', function (event) {
    if (isInViewport(findMe)) {
        console.log('In viewport!');
    } else {
    console.log('Nope...');
  }
}, false);

Answer 3

JavaScript 用于在元素滚动到视图中时对其进行动画处理的库。

https://scrollrevealjs.org/

如何延迟 html/css 加载直到项目在视口中

How to delay html/css load until item is in viewport

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viewport