javascript - 在jquery或javascript中的特定类之前计数元素(Count elements before a specific class in jquery or javascript)

Question

I have to count all classes with the name " loader " before the class " p16 " (for example).(我必须在类“ p16 ” 之前计算所有名称为“ loader ”的类。)

In this case the right answer would be: 4(在这种情况下，正确的答案是： 4) <div class="loader p12"></div> <div class="loader p13"></div> <div class="loader p14"></div> <div class="loader p15"></div> <div class="loader p16"></div> <div class="loader p17"></div> <div class="loader p18"></div> I tried serveral solutions:(我尝试了服务器解决方案：) var $slides = $('.loader'); var $current = $slides.find('.p5'); var index = $slides.index($current) + 1; var total = $slides.length; var n = $('.loader').index('.p5'); alert(n); alert(index); Here is a fiddle:(这是一个小提琴：) https://jsfiddle.net/mc184j7f/(https://jsfiddle.net/mc184j7f/) Thank you very much.(非常感谢你。)   ask by Lars Vegas translate from so

Answer 1

You could use prevAll()(您可以使用prevAll（）)

console.log($('.p16').prevAll('.loader').length) <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div class="loader p12"></div> <div class="loader p13"></div> <div class="loader p14"></div> <div class="loader p15"></div> <div class="loader p16"></div> <div class="loader p17"></div> <div class="loader p18"></div>