有一個(gè)需求是這這樣的，當(dāng)頁面加載完的時(shí)候，根據(jù)當(dāng)前頁面的URL，來判斷對(duì)應(yīng)的圖片資源是否存在，如果存在則就用這個(gè)對(duì)應(yīng)的圖片，如果不存在則使用默認(rèn)的圖片。
假設(shè)當(dāng)前頁面URL：https://www.example.com/somep...
規(guī)則對(duì)應(yīng)的圖片文件是someid.png,圖片的URL：https://imgs.example.com/imgs...
如果不存在這張圖片，則使用默認(rèn)的https://imgs.example.com/imgs...

這里的jquery 如何去判斷 https://imgs.example.com/imgs...？

var popup = (
    function() {
        var target = window.location.href;
        var currentFilename = window.location.pathname.split("/")[window.location.pathname.split("/").length - 1].split(".")[0];
        var currentPopupImg = 'https://imgs.example.com/' + currentFilename + '.png';
        var defautlPopupImg = 'https://imgs.example.com/default.png';
        var picContent = "";
        var checkPopupImgOnce = function() {
            $.ajax({
                url: currentPopupImg,
                 cache: false,
                dataType:"jsonp",
                type: 'GET',
                complete: function(response) {
                    if (response.status == 200) {
                        picContent = currentFilename;
                    } else {
                        changePopUpImgSrc();
                    }
                }
            });
        }
        var changePopUpImgSrc = function() {
            picContent = defautlPopupImg;
        }
        var showPopUp = function() {
            var flag = 0;
            layer.open({
                type: 1,
                title: false,
                closeBtn: 0,
                shade: 0,
                shadeClose: true,
                anim: 0,
                skin: 'popup',
                area: ['600px', '450px'],
                time: 12000,
                resize: false,
                btn: ['不再提醒', '稍后再說', '立即了解'],
                yes: function(index, layero) {
                    //按鈕【按鈕一】的回調(diào)
                    //永遠(yuǎn)關(guān)閉彈窗
                    flag = 1;
                    layer.closeAll();
                },
                btn2: function(index, layero) {
                    //按鈕【按鈕二】的回調(diào)
                    //$("#layui-layer1").hide();
                    //暫時(shí)關(guān)閉彈窗
                    flag = 0;
                    layer.close(index);
                },
                btn3: function(index, layero) {
                    //按鈕【按鈕三】的回調(diào)
                    //return false 開啟該代碼可禁止點(diǎn)擊該按鈕關(guān)閉
                    //打開快商通
                    //暫時(shí)關(guān)閉彈窗
                    flag = 0;
                    window.open('https://ad.example.com');
                    layer.close(index);
                },
                btnAlign: 'c',
                content: picContent,
                end: function() {
                    if (flag == 1) {
                        // 永遠(yuǎn)關(guān)閉彈窗
                        window.clearTimeout(timer);
                    } else {
                        timer = setTimeout(popup, 15000);
                    }
                }
            });
        }
        var pop = {
            checkimg: checkPopupImgOnce,
            showPopUp: showPopUp
        }
        return pop;
    })();
popup.checkimg();
popup.showPopUp();