下载文件名含有多个点号导致扩展名错误如何解决？

export const downloadFile = (fileUrl, fileName, errorCallback) => {
    try {
        const xhr = new XMLHttpRequest();
        xhr.open("get", fileUrl, true);
        xhr.responseType = "blob";
        xhr.send();
        xhr.onload = function () {
            if (this.status === 200 || this.status === 304) {
                const contentType = this.getResponseHeader("Content-Type");
                let ext = '';
                // 根据Content-Type设置扩展名，可根据实际情况补充更多类型
                if (contentType.includes('application/pdf')) {
                    ext = '.pdf';
                } else if (contentType.includes('application/zip')) {
                    ext = '.zip';
                } else if (contentType.includes('application/vnd.openxmlformats-officedocument.wordprocessingml.document')) {
                    ext = '.docx';
                }
                // ... 其他类型判断 ...

                // Content-Type无法判断时，使用原文件名，避免覆盖
                if(ext === ''){
                    const fileNameParts = fileName.split('.');
                    ext = fileNameParts.length > 1 ? '.' + fileNameParts.pop() : '';
                }

                const blob = new Blob([this.response], { type: contentType });
                const finalFileName = fileName + ext; // 使用Content-Type确定的扩展名

                if ("msSaveOrOpenBlob" in navigator) {
                    navigator.msSaveOrOpenBlob(blob, finalFileName);
                    return;
                }
                const url = URL.createObjectURL(blob);
                simulateClick(blob, finalFileName, "_blank");
                URL.revokeObjectURL(url);
            }
        };
        xhr.onerror = function () {
            errorCallback && errorCallback();
        };
    } catch (error) {
        errorCallback && errorCallback();
    }
};