具體實現(xiàn)：
    改變img-box中img的src打的同時能夠立刻同步到bgimg，以背景圖的形式展現(xiàn)，"background-image":"url($('.img-box img').attr('src').substring(0,20))"，這里的url要怎么寫
    
<div class="bgimg">

</div>
<div class="img-box">
    <img src="img/2.jpg" alt="">
</div>

$(function(){
        let h = document.documentElement.clientHeight;
        $(".bgimg").height(h) + "px";
        $(".bgimg").css({"background-image":"url($('.img-box img').attr('src').substring(0,20))"});
        console.log($('.img-box img').attr('src').substring(0,20));
            
        })