Why is the js of the same segment normal on PC but not on mobile?

html call code:

<div id="pgbtn" class="pgbtn_page">
      <a class="page_a" href="javascript：;" rel="forum.php?order={$_GET["order"]}&page=$ntpage" curpage="{$_G["page"]}" id="autopbn" totalpage="{$fynum}" picstyle="$_G[forum][picstyle]" forumdefstyle="$_G[cookie][forumdefstyle]"></a>
      <script type="text/javascript" src="{$_G[style][styleimgdir]}/js/exauto_ajax_page.js?{VERHASH}"></script>
    </div>

js file code:

(function() {

    var autopbn = $("autopbn");
    var nextpageurl = autopbn.getAttribute("rel").valueOf();
    var curpage = parseInt(autopbn.getAttribute("curpage").valueOf());
    var totalpage = parseInt(autopbn.getAttribute("totalpage").valueOf());
    var picstyle = parseInt(autopbn.getAttribute("picstyle").valueOf());
    var forumdefstyle = parseInt(autopbn.getAttribute("forumdefstyle").valueOf());
    picstyle = picstyle && !forumdefstyle;
    var autopagenum = 0;
    var maxpage = (curpage + autopagenum) > totalpage ? totalpage : (curpage + autopagenum);

    var loadstatus = 0;

    autopbn.onclick = function() {
        var oldloadstatus = loadstatus;
        loadstatus = 2;
        autopbn.innerHTML = ", ...";
        getnextpagecontent();
        loadstatus = oldloadstatus;
    };

    if(autopagenum > 0) {
        window.onscroll = function () {
            var curtop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
            if(curtop + document.documentElement.clientHeight + 500 >= document.documentElement.scrollHeight && !loadstatus) {
                loadstatus = 1;
                autopbn.innerHTML = ", ...";
                setTimeout(getnextpagecontent, 1000);
            }
        };
    }

    function getnextpagecontent() {

        if(curpage + 1 > totalpage) {
            window.onscroll = null;
            autopbn.innerHTML = "...";
            return;
        }
        if(loadstatus != 2 && curpage + 1 > maxpage) {
            autopbn.innerHTML = "";
            if(curpage + 1 > maxpage) {
                window.onscroll = null;
            }
            return;
        }
        curpagePP;
        var url = nextpageurl + "&t=" + parseInt((+new Date()/1000)/(Math.random()*1000));
        var x = new Ajax("HTML");
        x.get(url, function (s) {
            s = s.replace(/\n|\r/g, "");
            if(s.indexOf("id=\"autopbn\"") == -1) {
                $("autopbn").innerHTML = "...";
                window.onscroll = null;
            }

            if(!picstyle) {
                var tableobj = $("thread-list");
                var nexts = s.match(/\<article id="normalthread_(\d+)" class="topic-visited"\>(.+?)\<\/article>/g);
                for(i in nexts) {
                    if(i == "index" || i == "lastIndex") {
                        continue;
                    }
                    var insertid = nexts[i].match(/<article id="normalthread_(\d+)" class="topic-visited"\>/);
                    if(!$("normalthread_" + insertid[1])) {

                        var newbody = document.createElement("article");
                        tableobj.appendChild(newbody);
                        var div = document.createElement("div");
                        div.innerHTML = "<div>" + nexts[i] + "</div>";
                        tableobj.replaceChild(div.childNodes[0].childNodes[0], tableobj.lastChild);
                    }
                }
            } else {
                var nexts = s.match(/\<li style="width:\d+px;" id="picstylethread_(\d+)"\>(.+?)\<\/li\>/g);
                for(i in nexts) {
                    var insertid = nexts[i].match(/id="picstylethread_(\d+)"\>/);
                    if(!$("picstylethread_" + insertid[1])) {
                        $("threadlist_picstyle").innerHTML += nexts[i];
                    }
                }
            }
            var pageinfo = s.match(/\<div id="fd_page_bottom" class="panel-footer clearfix"\>(.+?)\<\/div\>/);
            nextpageurl = nextpageurl.replace(/&page=\d+/, "&page=" + (curpage + 1));

            $("fd_page_bottom").innerHTML = pageinfo[1];
            if(curpage + 1 > totalpage) {
                autopbn.innerHTML = "...";
            } else {
                autopbn.innerHTML = "";
            }
            loadstatus = 0;
        });
    }

})();