js 正则表达式如何替换匹配到的第二个元素，不需要全部替换

    function initiallist(a,b) { //listsData 初始
        var listData = [];
        for (x in xArgs) {
            for (y in xArgs[x]) {
                listData.push('<li mclassify='+xArgs[x][y].classify+' class="option"><a href="javascript:void(0);"><i class="sidebar-arrow"></i><span class="sort-of-term">' + xArgs[x][y].classify + '</span><small class="sort-of-term">不限</small></a></li>')
            }
        }
        var listfilter = listData.join("");
        //如何修改字符串中 第二<small class="sort-of-term">不限</small>
        if(a!==undefined){
            var news='<small class="sort-of-term">不限</small>';
            var re=/"news+"/g;
            var regindex=listfilter.search(re)
            var listfilter = listfilter.replace(regindex,'<small class="sort-of-term">'+被替换的值+'</small>')    //需替换第a个匹配的值
        }

    }

//for 循环listfilter结果为
/*<li mclassify="时间" class="option">

---

    var text="AbcdAefgAkmnAsbhAert"
    var text1=""
    var arr=text.split(/A/)
    for(var i=3,l=arr.length;i<l;i++){
        text1+="A"+arr[i]
    }
    console.log("A"+arr[1]+"_"+arr[2]+text1)