/*
 *downloadPdf 下載工具
 * url 下載路徑
 * name 保存的 名字
 * 
 * */
//download.js v3.0, by dandavis; 2008-2014. [CCBY2] see官網(wǎng) 地址http://danml.com/download.html
// data can be a string, Blob, File, or dataURL
function downloadFile(url, name) {
    var x = new XMLHttpRequest();
    x.open("GET", url, true);
    x.responseType = 'blob';
    x.onload = function(e) {
        download(x.response, name || 'shanyanwt.pdf', "image/png");
    };
    x.send();
 
}
 
function download(data, strFileName, strMimeType) {
 
    var self = window, // this script is only for browsers anyway...
        u = "application/octet-stream", // this default mime also triggers iframe downloads
        m = strMimeType || u,
        x = data,
        D = document,
        a = D.createElement("a"),
        z = function(a) {
            return String(a);
        },
 
        B = self.Blob || self.MozBlob || self.WebKitBlob || z,
        BB = self.MSBlobBuilder || self.WebKitBlobBuilder || self.BlobBuilder,
        fn = strFileName || "download",
        blob,
        b,
        ua,
        fr;
 
    //if(typeof B.bind === 'function' ){ B=B.bind(self); }
 
    if(String(this) === "true") { //reverse arguments, allowing download.bind(true, "text/xml", "export.xml") to act as a callback
        x = [x, m];
        m = x[0];
        x = x[1];
    }
 
    //go ahead and download dataURLs right away
    if(String(x).match(/^data\:[\w+\-]+\/[\w+\-]+[,;]/)) {
        return navigator.msSaveBlob ? // IE10 can't do a[download], only Blobs:
            navigator.msSaveBlob(d2b(x), fn) :
            saver(x); // everyone else can save dataURLs un-processed
    } //end if dataURL passed?
 
    try {
 
        blob = x instanceof B ?
            x :
            new B([x], {
                type: m
            });
    } catch(y) {
        if(BB) {
            b = new BB();
            b.append([x]);
            blob = b.getBlob(m); // the blob
        }
 
    }
 
    function d2b(u) {
        var p = u.split(/[:;,]/),
            t = p[1],
            dec = p[2] == "base64" ? atob : decodeURIComponent,
            bin = dec(p.pop()),
            mx = bin.length,
            i = 0,
            uia = new Uint8Array(mx);
 
        for(i; i < mx; ++i) uia[i] = bin.charCodeAt(i);
 
        return new B([uia], {
            type: t
        });
    }
 
    function saver(url, winMode) {
 
        if('download' in a) { //html5 A[download]           
            a.href = url;
            a.setAttribute("download", fn);
            a.innerHTML = "downloading...";
            D.body.appendChild(a);
            setTimeout(function() {
                a.click();
                D.body.removeChild(a);
                if(winMode === true) {
                    setTimeout(function() {
                        self.URL.revokeObjectURL(a.href);
                    }, 250);
                }
            }, 66);
            return true;
        }
 
        //do iframe dataURL download (old ch+FF):
        var f = D.createElement("iframe");
        D.body.appendChild(f);
        if(!winMode) { // force a mime that will download:
            url = "data:" + url.replace(/^data:([\w\/\-\+]+)/, u);
        }
 
        f.src = url;
        setTimeout(function() {
            D.body.removeChild(f);
        }, 333);
 
    } //end saver 
 
    if(navigator.msSaveBlob) { // IE10+ : (has Blob, but not a[download] or URL)
        return navigator.msSaveBlob(blob, fn);
    }
 
    if(self.URL) { // simple fast and modern way using Blob and URL:
        saver(self.URL.createObjectURL(blob), true);
    } else {
        // handle non-Blob()+non-URL browsers:
        if(typeof blob === "string" || blob.constructor === z) {
            try {
                return saver("data:" + m + ";base64," + self.btoa(blob));
            } catch(y) {
                return saver("data:" + m + "," + encodeURIComponent(blob));
            }
        }
 
        // Blob but not URL:
        fr = new FileReader();
        fr.onload = function(e) {
            saver(this.result);
        };
        fr.readAsDataURL(blob);
    }
    return true;
} /* end download() */
export default {
    download,
    downloadFile
}
export {
    download,
    downloadFile
}

html

<button  @click="todownload(pdfurl)" >下載</button>

import {download} from '../../utils/download'
     async todownload( data){
      var x = new XMLHttpRequest();
      x.open("GET", data, true);
      x.responseType = 'blob';
      x.onload = function(e) {
        download(x.response, name || 'shanyanwt.pdf', "image/png");
      };
      x.send();
      return false
    },