swiper官網中（https://www.swiper.com.cn/api/properties/310.html）提到

就是說如果寫了 loop：true是的時候，會在迴圈完切換到第一張，但是獲取索引就是realIndex

下面上程式碼

 <div class="main-left">
                    <div class="swiper-container swiper-banner">
                        <div class="swiper-wrapper">
                            <
 
div class="swiper-slide slide-items">
                                <a class="slide-a">
                                    <img
                                        src="http://www.chooseauto.com.cn/image2/2019/11/23/CCD7D1D053B645F7B8C11BC0F75116FA.jpg">

                                </
 
a>
                                <div class="slide-tit">
                                    <a href="/zixun/hangye/307046.shtml" target="_blank">新“雙積分”政策指向何方</a>
                                </div>
                            </div>

                            <
 
div class="swiper-slide slide-items"> <a class="slide-a">
                                    <img
                                        src="http://www.chooseauto.com.cn/image3/2020/7/6/25FE83B2DF3549A99C9D57A48D8E6236.png">

                                </a>
                                <div class="slide-tit">
                                    <a href="/zixun/hangye/307046.shtml" target="_blank">新“雙積分”政策指向何方</a>
                                </div>
                            </div>
                            <div class="swiper-slide slide-items"> <a class="slide-a">
                                    <img
                                        src="http://www.chooseauto.com.cn/image4/2020/7/7/C369CDF2C4C14E4EA1146F872138F999.jpg">

                                </a>
                                <div class="slide-tit">
                                    <a href="/zixun/hangye/307046.shtml" target="_blank">新“雙積分”政策指向何方</a>
                                </div>
                            </div>
                        </div>
                       <div class="swiper-button-prev arrow-left" ></div> 
                        <!--左箭頭。如果放置在swiper-container外面，需要自定義樣式。-->
                        <div class="swiper-button-next arrow-right"></div> 
                        <!--右箭頭。如果放置在swiper-container外面，需要自定義樣式。-->
                    </div>
                    <div class="index-wrap"> <span class="active-num">1</span></div>
                </div>

js

var mySwiper = new Swiper('.swiper-banner', {
    autoplay: true,//自動播放
    loop: true,//迴圈播放
    pagination: {
        el: '#banner_paination',
    },
    navigation: {
        nextEl: '.swiper-button-next',
        prevEl: '.swiper-button-prev',
    },
    on:{
        slideChangeTransitionEnd:function(){
            //獲取當前的索引
            $(".active-num").html(this.realIndex + 1);
        }
    }

})

效果圖