javascript - 如何修改这个 jQuery 脚本，该脚本仅在用户向下滚动到它时才进行计数？

Question

我偶然发现了这个片段，它对于一个网站来说在 jQuery 中的数量最多为 here .

我如何修改它以等待开始计数，直到用户向下滚动到类“counter col_fourth”或另一个类？

我知道我需要使用滚动类，但我不知道该怎么做。

我正在考虑使用类似 jQuery - How do I get my counter to load only when in view? 的东西

//由 Sayed Rafeeq 创建

(function ($) {


$.fn.countTo = function (options) {
    options = options || {};

    return $(this).each(function () {
        // set options for current element
        var settings = $.extend({}, $.fn.countTo.defaults, {
            from:            $(this).data('from'),
            to:              $(this).data('to'),
            speed:           $(this).data('speed'),
            refreshInterval: $(this).data('refresh-interval'),
            decimals:        $(this).data('decimals')
        }, options);

        // how many times to update the value, and how much to increment the value on each update
        var loops = Math.ceil(settings.speed / settings.refreshInterval),
            increment = (settings.to - settings.from) / loops;

        // references & variables that will change with each update
        var self = this,
            $self = $(this),
            loopCount = 0,
            value = settings.from,
            data = $self.data('countTo') || {};

        $self.data('countTo', data);

        // if an existing interval can be found, clear it first
        if (data.interval) {
            clearInterval(data.interval);
        }
        data.interval = setInterval(updateTimer, settings.refreshInterval);

        // initialize the element with the starting value
        render(value);

        function updateTimer() {
            value += increment;
            loopCount++;

            render(value);

            if (typeof(settings.onUpdate) == 'function') {
                settings.onUpdate.call(self, value);
            }

            if (loopCount >= loops) {
                // remove the interval
                $self.removeData('countTo');
                clearInterval(data.interval);
                value = settings.to;

                if (typeof(settings.onComplete) == 'function') {
                    settings.onComplete.call(self, value);
                }
            }
        }

        function render(value) {
            var formattedValue = settings.formatter.call(self, value, settings);
            $self.html(formattedValue);
        }
    });
};

$.fn.countTo.defaults = {
    from: 0,               // the number the element should start at
    to: 0,                 // the number the element should end at
    speed: 1000,           // how long it should take to count between the target numbers
    refreshInterval: 100,  // how often the element should be updated
    decimals: 0,           // the number of decimal places to show
    formatter: formatter,  // handler for formatting the value before rendering
    onUpdate: null,        // callback method for every time the element is updated
    onComplete: null       // callback method for when the element finishes updating
};

function formatter(value, settings) {
    return value.toFixed(settings.decimals);
}
}(jQuery));

jQuery(function ($) {
  // custom formatting example
  $('#count-number').data('countToOptions', {
    formatter: function (value, options) {
      return value.toFixed(options.decimals).replace(/\B(?=(?:\d{3})+(?!\d))/g, ',');
    }
  });

  // start all the timers
  $('.timer').each(count);  

  function count(options) {
    var $this = $(this);
    options = $.extend({}, options || {}, $this.data('countToOptions') || {});
    $this.countTo(options);
  }
});

Answer 1

所有借用的小型模组，以便链接的 CodePen JS 不会在加载时自动运行(timerNew 类而不是计时器)

//from http://stackoverflow.com/a/33138553/4946681
function isScrolledIntoView(elem) {
  var $elem = $(elem);
  var $window = $(window);

  var docViewTop = $window.scrollTop();
  var docViewBottom = docViewTop + $window.height();

  var elemTop = $elem.offset().top;
  var elemBottom = elemTop + $elem.height();

  return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}

$(window).on('scroll', function () {
    if (isScrolledIntoView('.wrapper')) {
        $('.timerNew').countTo();
        $(window).off('scroll');
    }
});

.spacer {
  height: 2000px;
}

<link href="https://netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.min.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<link href="https://codepen.io/syedrafeeq/pen/rcfsJ.css" rel="stylesheet"/>
<script src="https://codepen.io/syedrafeeq/pen/rcfsJ.js"></script>

<h1>JQUERY NUMBER ANIMATION</h1>
<h3>jQuery counter to count up to a target number</h3>
<div class="spacer">&nbsp;</div>
<div class="wrapper">
    <div class="counter col_fourth">
      <i class="fa fa-code fa-2x"></i>
      <h2 class="timerNew count-title" id="count-number" data-to="300" data-speed="1500"></h2>
       <p class="count-text ">SomeText GoesHere</p>
    </div>

    <div class="counter col_fourth">
      <i class="fa fa-coffee fa-2x"></i>
      <h2 class="timerNew count-title" id="count-number" data-to="17870" data-speed="1500"></h2>
      <p class="count-text ">SomeText GoesHere</p>
    </div>

    <div class="counter col_fourth">
      <i class="fa fa-lightbulb-o fa-2x"></i>
      <h2 class="timerNew count-title" id="count-number" data-to="847" data-speed="1500"></h2>
      <p class="count-text ">SomeText GoesHere</p>
    </div>

    <div class="counter col_fourth end">
      <i class="fa fa-bug fa-2x"></i>
      <h2 class="timerNew count-title" id="count-number" data-to="157" data-speed="1500"></h2>
      <p class="count-text ">SomeText GoesHere</p>
    </div>
</div>