js方法（适用于后台返回类型为url链接）

function getDownloadMb(e) {
    const x = new window.XMLHttpRequest();
    x.open('GET', e.currentTarget.dataset.fileUrl, true);
    x.responseType = 'blob';
    const fileName = e.currentTarget.dataset.fileName
    const fileUrl = e.currentTarget.dataset.fileUrl
    x.onload = () => {
        const url = window.URL.createObjectURL(x.response);
        const a = document.createElement('a');
        a.href = url;
        if (!fileName || fileName == 'null') {
            a.download = fileUrl
        } else {
            a.download = fileName;
        }
        a.click(); 

    };
    x.send();
}