JQuery：当元素在视图中时触发动作

Question

在我网站的页脚中，我使用 counUp.js（链接：http://inorganik.github.io/countUp.js/）计算三个数字。我在网站底部添加了这段代码：

   <script type="text/javascript">
          var c1 = new countUp("upnum1", 1, 27, 0, 4);
          var c2 = new countUp("upnum2", 1, 10, 0, 4);
          var c3 = new countUp("upnum3", 1, 27, 0, 4);
          var c4 = new countUp("upnum4", 1, 1000, 0, 4);
          window.onload = function() {
            c1.start();
            c2.start();
            c3.start();
            c4.start();
          }
    </script>

这很好用，但当然会在页面加载后开始计数。当数字的包含 div 处于“视图中”而不是加载页面时，我如何设法触发此效果？尝试了几个 jQuery 的东西，但找不到一个可行的解决方案......谢谢！

Answer 1

有一个简单的检查来查看元素是否在视口中。

您可以选择使用插件或纯 JQuery。

相关HTML：

<div id="inViewport">Is this in the viewport?</div>

纯 JQuery ：

这里是这个的小提琴： http://jsfiddle.net/zWtkc/1/

$.fn.isOnScreen = function(){

    var win = $(window);

    var viewport = {
        top : win.scrollTop(),
        left : win.scrollLeft()
    };
    viewport.right = viewport.left + win.width();
    viewport.bottom = viewport.top + win.height();

    var bounds = this.offset();
    bounds.right = bounds.left + this.outerWidth();
    bounds.bottom = bounds.top + this.outerHeight();

    return (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));

};

$(document).ready(function(){
    $(window).scroll(function(){
        if ($('#inViewport').isOnScreen()) {
            // The element is visible, do something
            alert("in viewport!");
        } else {
            // The element is NOT visible, do something else
        }
    });
});

插件：

你可以使用这个插件：https://github.com/teamdf/jquery-visible/

$(document).ready(function(){
    if ($('#inViewport').visible(true)) {
        // The element is visible, do something
    } else {
        // The element is NOT visible, do something else
    }
});

或者您可以使用这个插件：http://www.appelsiini.net/projects/viewport，它允许视口选择器，您的代码将如下所示：

$('#inViewport:in-viewport').doSomething();

Answer 2

这就是我使用这个插件的方式：https://github.com/protonet/jquery.inview

var options = {
    useEasing : true, 
    useGrouping : true, 
    separator : ',', 
    decimal : '.', 
    prefix : '', 
    suffix : '' 
    };
    var c1 = new CountUp("a1", 0, 1000, 0, 5, options);
    var c2 = new CountUp("a2", 0, 1000, 0, 5, options);
    var c3 = new CountUp("a3", 0, 1000, 0, 5, options);
    var c4 = new CountUp("a4", 0, 1000, 0, 5, options);
    var c5 = new CountUp("a5", 0, 1000, 0, 5, options);
    var c6 = new CountUp("a6", 0, 1000, 0, 5, options);

    $('#counters').one('inview', function(event, isInView) {

    c1.start();
    c2.start();
    c3.start();
    c4.start();
    c5.start();
    c6.start();
});

Answer 3

这是我在元素开始进入视口时运行函数的代码。

---

您可以通过单击jfiddle 查看正在运行的代码

var counterTeaserL = $('.go-counterTeaser');
var winHeight = $(window).height();
if (counterTeaserL.length) {
    var firEvent = false,
        objectPosTop = $('.go-counterTeaser').offset().top;

        //when element shows at bottom
        var elementViewInBottom = objectPosTop - winHeight;
    $(window).on('scroll', function() {
        var currentPosition = $(document).scrollTop();
        //when element position starting in viewport
      if (currentPosition > elementViewInBottom && firEvent === false) {
        firEvent = true;
        animationCounter();
      }   
    });
}

//counter function will animate by using external js also add seprator "."
 function animationCounter(){
        $('.numberBlock h2').each(function () {
            var comma_separator_number_step =           $.animateNumber.numberStepFactories.separator('.');
            var counterValv = $(this).text();
            $(this).animateNumber(
                {
                  number: counterValv,
                  numberStep: comma_separator_number_step
                }
            );
        });
    }


https://jsfiddle.net/uosahmed/frLoxm34/9/