jquery计数器在视口上激活

Question

我已从https://bestjquery.com/tutorial/counter/demo155/ 复制了此计数器代码 它工作得很好，但是当我把它放在页面底部时，它会立即启动并在我滚动查看它之前完成计数。 我希望它出现在视口上时开始计数。 谢谢你。 这是代码：

$(document).ready(function() {
  $('.counter-value').each(function() {
    $(this).prop('Counter', 0).animate({
      Counter: $(this).text()
    }, {
      duration: 3500,
      easing: 'swing',
      step: function(now) {
        $(this).text(Math.ceil(now));
      }
    });
  });
});

.counter {
  background: #fff;
  font-family: 'Noto Sans JP', sans-serif;
  text-align: center;
  width: 210px;
  padding: 0 0 25px;
  margin: 0 auto 15px;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.15);
  position: relative;
}

.counter:before {
  content: "";
  background: #fff;
  width: 30px;
  height: 30px;
  border-radius: 5px 0;
  box-shadow: 4px 4px 4px rgba(0, 0, 0, 0.07);
  transform: translateX(-50%) rotate(45deg);
  position: absolute;
  bottom: -15px;
  left: 50%;
}

.counter .counter-value {
  color: #fff;
  background: linear-gradient(to right, #19bbd2, #2778ee);
  font-size: 38px;
  font-weight: 300;
  padding: 0 0 3px;
  margin: 0 0 25px;
  border-radius: 10px 10px 0 0;
  display: block;
}

.counter h3 {
  color: #2778ee;
  font-size: 18px;
  font-weight: 900;
  letter-spacing: 0.5px;
  text-transform: capitalize;
  margin: 0 0 25px;
}

.counter .counter-icon {
  color: #fff;
  background: linear-gradient(to right, #19bbd2, #2778ee);
  font-size: 40px;
  line-height: 60px;
  width: 65px;
  height: 65px;
  margin: 0 auto;
  border-radius: 10px;
}

.counter.purple .counter-value,
.counter.purple .counter-icon {
  background: linear-gradient(to right, #8f70e7, #c452ef);
}

.counter.purple h3 {
  color: #c452ef;
}

.counter.magenta .counter-value,
.counter.magenta .counter-icon {
  background: linear-gradient(to right, #e84a94, #ae379b);
}

.counter.magenta h3 {
  color: #ae379b;
}

.counter.yellow .counter-value,
.counter.yellow .counter-icon {
  background: linear-gradient(to right, #fecb4b, #e69814);
}

.counter.yellow h3 {
  color: #e69814;
}

@media screen and (max-width:990px) {
  .counter {
    margin-bottom: 45px;
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<div class="container">
  <div class="row">
    <div class="col-md-3 col-sm-6">
      <div class="counter">
        <span class="counter-value">343</span>
        <h3>Web Designing</h3>
        <div class="counter-icon">
          <i class="fa fa-briefcase"></i>
        </div>
      </div>
    </div>
    <div class="col-md-3 col-sm-6">
      <div class="counter purple">
        <span class="counter-value">324</span>
        <h3>Web Development</h3>
        <div class="counter-icon">
          <i class="fa fa-globe"></i>
        </div>
      </div>
    </div>
  </div>
</div>

Answer 1

尝试如下。在 cmets 中添加描述。

1. 在span 中添加额外的类pending 和class="counter-value"，如<span class="counter-value pending">324</span>。这个pending 类用于检查动画是否已经开始。如果它已经开始，那么我们不想重新设置它的动画。
2. 在脚本中添加了新函数setAnimation()。
3. 使用Utility Function 来检查元素是否可见。引用自How to check if element is visible after scrolling?。
4. 添加滚动事件并在滚动时调用setAnimation()。

---

setAnimation 函数。

// create new function which will trigger your animation
function setAnimation() {
  // add additional class pending to your .counter-value element to check whether animation is pending or not
  // retrieve only pending elements and loop over it
  $('.counter-value.pending').each(function() {
    // check if element is in view and visible
    var isElementInView = Utils.isElementInView($(this), false);    
    if (isElementInView) {
      // if visible then remove class pending so it won't animate multiple times
      $(this).removeClass('pending');
      // initialize animation
      $(this).prop('Counter', 0).animate({
        Counter: $(this).text()
      }, {
        duration: 3500,
        easing: 'swing',
        step: function(now) {
          $(this).text(Math.ceil(now));
        }
      });
    }
  });
}

试试下面的整个代码。 注意：添加<div class="container" style="height:200px;"></div> 仅用于测试目的。

$(document).ready(function() {
  // call newly created function
  setAnimation();
});

// add scroll event to check for animation on scroll
$(document).scroll(function() {
  // call newly created function
  setAnimation();
});

// Create new function which will trigger your animation
function setAnimation() {
  // add additional class pending to your .counter-value element to check whether animation is pending or not
  // retrieve only pending elements and loop over it
  $('.counter-value.pending').each(function() {
    // check if element is in view and visible
    var isElementInView = Utils.isElementInView($(this), false);    
    if (isElementInView) {
      // if visible then remove class pending so it won't animate multiple times
      $(this).removeClass('pending');
      // initialize animation
      $(this).prop('Counter', 0).animate({
        Counter: $(this).text()
      }, {
        duration: 3500,
        easing: 'swing',
        step: function(now) {
          $(this).text(Math.ceil(now));
        }
      });
    }
  });
}

// Added util code from https://stackoverflow.com/questions/487073/how-to-check-if-element-is-visible-after-scrolling
function Utils() {

}

Utils.prototype = {
  constructor: Utils,
  isElementInView: function(element, fullyInView) {
    var pageTop = $(window).scrollTop();
    var pageBottom = pageTop + $(window).height();
    var elementTop = $(element).offset().top;
    var elementBottom = elementTop + $(element).height();

    if (fullyInView === true) {
      return ((pageTop < elementTop) && (pageBottom > elementBottom));
    } else {
      return ((elementTop <= pageBottom) && (elementBottom >= pageTop));
    }
  }
};

var Utils = new Utils();

.counter {
  background: #fff;
  font-family: 'Noto Sans JP', sans-serif;
  text-align: center;
  width: 210px;
  padding: 0 0 25px;
  margin: 0 auto 15px;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.15);
  position: relative;
}

.counter:before {
  content: "";
  background: #fff;
  width: 30px;
  height: 30px;
  border-radius: 5px 0;
  box-shadow: 4px 4px 4px rgba(0, 0, 0, 0.07);
  transform: translateX(-50%) rotate(45deg);
  position: absolute;
  bottom: -15px;
  left: 50%;
}

.counter .counter-value {
  color: #fff;
  background: linear-gradient(to right, #19bbd2, #2778ee);
  font-size: 38px;
  font-weight: 300;
  padding: 0 0 3px;
  margin: 0 0 25px;
  border-radius: 10px 10px 0 0;
  display: block;
}

.counter h3 {
  color: #2778ee;
  font-size: 18px;
  font-weight: 900;
  letter-spacing: 0.5px;
  text-transform: capitalize;
  margin: 0 0 25px;
}

.counter .counter-icon {
  color: #fff;
  background: linear-gradient(to right, #19bbd2, #2778ee);
  font-size: 40px;
  line-height: 60px;
  width: 65px;
  height: 65px;
  margin: 0 auto;
  border-radius: 10px;
}

.counter.purple .counter-value,
.counter.purple .counter-icon {
  background: linear-gradient(to right, #8f70e7, #c452ef);
}

.counter.purple h3 {
  color: #c452ef;
}

.counter.magenta .counter-value,
.counter.magenta .counter-icon {
  background: linear-gradient(to right, #e84a94, #ae379b);
}

.counter.magenta h3 {
  color: #ae379b;
}

.counter.yellow .counter-value,
.counter.yellow .counter-icon {
  background: linear-gradient(to right, #fecb4b, #e69814);
}

.counter.yellow h3 {
  color: #e69814;
}

@media screen and (max-width:990px) {
  .counter {
    margin-bottom: 45px;
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<div class="container" style="height:200px;"></div>
<div class="container">
  <div class="row">
    <div class="col-md-3 col-sm-6">
      <div class="counter">
        <span class="counter-value pending">343</span>
        <h3>Web Designing</h3>
        <div class="counter-icon">
          <i class="fa fa-briefcase"></i>
        </div>
      </div>
    </div>
    <div class="col-md-3 col-sm-6">
      <div class="counter purple">
        <span class="counter-value pending">324</span>
        <h3>Web Development</h3>
        <div class="counter-icon">
          <i class="fa fa-globe"></i>
        </div>
      </div>
    </div>
  </div>
</div>