项目中的附件列表，通常情况都需要提供下载、删除的功能，功能本身没有什么要说的，都是基本功能，使用浏览器的的下载功能，也都是用window.open(url)，或者window.location.href=url的方式，url即为附件下载接口，浏览器自动解析，如果是图片、视频、txt等格式的会直接预览文件，而不是像docx、xlsx一样直接下载，项目中为了功能明确，将预览单独加了一个查看按钮，下载按钮要实现无论什么文件格式都直接下载。
有两种方式处理：
一.后台接口层面处理：（比较常见）
响应头中添加标识：
Response.AddHeader("Content-Disposition", "attachment; filename=" +
HttpUtility.UrlEncode(annotation.FileName, System.Text.Encoding.UTF8));
添加后，浏览器就会全都直接下载，不区分文件格式
二.前端JS使用XMLHttpRequest结合download.js处理
1）首先页面中需要引用download.js
2）公共方法
/* * 使用download.js 强制浏览器下载图片、视频等文件 * @param {any} url url链接地址 * @param {any} strFileName 文件名 * @param {any} strMimeType 文件类型 * dzl * 2020年5月8日 */ function downloadfile(url, strFileName, strMimeType) { var xmlHttp = null; if (window.ActiveXObject) { // IE6, IE5 浏览器执行代码 xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) { // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码 xmlHttp = new XMLHttpRequest(); } //2.如果实例化成功，就调用open（）方法： if (xmlHttp != null) { xmlHttp.open("get", url, true); xmlHttp.responseType = 'blob';//关键 xmlHttp.send(); xmlHttp.onreadystatechange = doResult; //设置回调函数 } function doResult() { if (xmlHttp.readyState == 4) { //4表示执行完成 if (xmlHttp.status == 200) { //200表示执行成功 download(xmlHttp.response, strFileName, strMimeType); } } } }
注意： xmlHttp.responseType = 'blob';是关键，必须要设置
3）下载按钮点击事件中调用公共方法
downloadfile(url, filename, getFileType(filename))
附上根据文件名的尾缀 返回文件类型的公共方法:
/* * 根据文件名的尾缀 返回文件类型 * @param {any} fileName 文件名 * dzl * 2020年5月9日 */ function getFileType(fileName) { // 后缀获取 let suffix = ''; // 获取类型结果 let result = ''; try { const flieArr = fileName.split('.'); suffix = flieArr[flieArr.length - 1]; } catch (err) { suffix = ''; } // fileName无后缀返回 false if (!suffix) { return false; } suffix = suffix.toLocaleLowerCase(); // 图片格式 const imglist = ['png', 'jpg', 'jpeg', 'bmp', 'gif']; // 进行图片匹配 result = imglist.find(item => item === suffix); if (result) { return 'image'; } // 匹配txt const txtlist = ['txt']; result = txtlist.find(item => item === suffix); if (result) { return 'txt'; } // 匹配 excel const excelist = ['xls', 'xlsx']; result = excelist.find(item => item === suffix); if (result) { return 'excel'; } // 匹配 word const wordlist = ['doc', 'docx']; result = wordlist.find(item => item === suffix); if (result) { return 'word'; } // 匹配 pdf const pdflist = ['pdf']; result = pdflist.find(item => item === suffix); if (result) { return 'pdf'; } // 匹配 ppt const pptlist = ['ppt', 'pptx']; result = pptlist.find(item => item === suffix); if (result) { return 'ppt'; } // 匹配 视频 const videolist = ['mp4', 'm2v', 'mkv', 'rmvb', 'wmv', 'avi', 'flv', 'mov', 'm4v']; result = videolist.find(item => item === suffix); if (result) { return 'video'; } // 匹配 音频 const radiolist = ['mp3', 'wav', 'wmv']; result = radiolist.find(item => item === suffix); if (result) { return 'radio'; } // 其他 文件类型 return 'other'; }
download.js源码
//download.js v4.21, by dandavis; 2008-2018. [MIT] see for tests/usage // v1 landed a FF+Chrome compatible way of downloading strings to local un-named files, upgraded to use a hidden frame and optional mime // v2 added named files via a[download], msSaveBlob, IE (10+) support, and window.URL support for larger+faster saves than dataURLs // v3 added dataURL and Blob Input, bind-toggle arity, and legacy dataURL fallback was improved with force-download mime and base64 support. 3.1 improved safari handling. // v4 adds AMD/UMD, commonJS, and plain browser support // v4.1 adds url download capability via solo URL argument (same domain/CORS only) // v4.2 adds semantic variable names, long (over 2MB) dataURL support, and hidden by default temp anchors // https://github.com/rndme/download (function (root, factory) { if (typeof define === 'function' && define.amd) { // AMD. Register as an anonymous module. define([], factory); } else if (typeof exports === 'object') { // Node. Does not work with strict CommonJS, but // only CommonJS-like environments that support module.exports, // like Node. module.exports = factory(); } else { // Browser globals (root is window) root.download = factory(); } }(this, function () { return function download(data, strFileName, strMimeType) { var self = window, // this script is only for browsers anyway... defaultMime = "application/octet-stream", // this default mime also triggers iframe downloads mimeType = strMimeType || defaultMime, payload = data, url = !strFileName && !strMimeType && payload, anchor = document.createElement("a"), toString = function(a){return String(a);}, myBlob = (self.Blob || self.MozBlob || self.WebKitBlob || toString), fileName = strFileName || "download", blob, reader; myBlob= myBlob.call ? myBlob.bind(self) : Blob ; if(String(this)==="true"){ //reverse arguments, allowing download.bind(true, "text/xml", "export.xml") to act as a callback payload=[payload, mimeType]; mimeType=payload[0]; payload=payload[1]; } if(url && url.length< 2048){ // if no filename and no mime, assume a url was passed as the only argument fileName = url.split("https://www.jb51.net/").pop().split("?")[0]; anchor.href = url; // assign href prop to temp anchor if(anchor.href.indexOf(url) !== -1){ // if the browser determines that it's a potentially valid url path: var ajax=new XMLHttpRequest(); ajax.open( "GET", url, true); ajax.responseType = 'blob'; ajax.onload= function(e){ download(e.target.response, fileName, defaultMime); }; setTimeout(function(){ ajax.send();}, 0); // allows setting custom ajax headers using the return: return ajax; } // end if valid url? } // end if url? //go ahead and download dataURLs right away if(/^data:([\w+-]+\/[\w+.-]+)?[,;]/.test(payload)){ if(payload.length > (1024*1024*1.999) && myBlob !== toString ){ payload=dataUrlToBlob(payload); mimeType=payload.type || defaultMime; }else{ return navigator.msSaveBlob ? // IE10 can't do a[download], only Blobs: navigator.msSaveBlob(dataUrlToBlob(payload), fileName) : saver(payload) ; // everyone else can save dataURLs un-processed } }else{//not data url, is it a string with special needs? if(/([\x80-\xff])/.test(payload)){ var i=0, tempUiArr= new Uint8Array(payload.length), mx=tempUiArr.length; for(i;i<mx;++i) tempUiArr[i]= payload.charCodeAt(i); payload=new myBlob([tempUiArr], {type: mimeType}); } } blob = payload instanceof myBlob ? payload : new myBlob([payload], {type: mimeType}) ; function dataUrlToBlob(strUrl) { var parts= strUrl.split(/[:;,]/), type= parts[1], indexDecoder = strUrl.indexOf("charset")>0 ? 3: 2, decoder= parts[indexDecoder] == "base64" ? atob : decodeURIComponent, binData= decoder( parts.pop() ), mx= binData.length, i= 0, uiArr= new Uint8Array(mx); for(i;i<mx;++i) uiArr[i]= binData.charCodeAt(i); return new myBlob([uiArr], {type: type}); } function saver(url, winMode){ if ('download' in anchor) { //html5 A[download] anchor.href = url; anchor.setAttribute("download", fileName); anchor.className = "download-js-link"; anchor.innerHTML = "downloading..."; anchor.style.display = "none"; anchor.addEventListener('click', function(e) { e.stopPropagation(); this.removeEventListener('click', arguments.callee); }); document.body.appendChild(anchor); setTimeout(function() { anchor.click(); document.body.removeChild(anchor); if(winMode===true){setTimeout(function(){ self.URL.revokeObjectURL(anchor.href);}, 250 );} }, 66); return true; } // handle non-a[download] safari as best we can: if(/(Version)\/(\d+)\.(\d+)(?:\.(\d+))?.*Safari\//.test(navigator.userAgent)) { if(/^data:/.test(url)) url="data:"+url.replace(/^data:([\w\/\-\+]+)/, defaultMime); if(!window.open(url)){ // popup blocked, offer direct download: if(confirm("Displaying New Document\n\nUse Save As... to download, then click back to return to this page.")){ location.href=url; } } return true; } //do iframe dataURL download (old ch+FF): var f = document.createElement("iframe"); document.body.appendChild(f); if(!winMode && /^data:/.test(url)){ // force a mime that will download: url="data:"+url.replace(/^data:([\w\/\-\+]+)/, defaultMime); } f.src=url; setTimeout(function(){ document.body.removeChild(f); }, 333); }//end saver if (navigator.msSaveBlob) { // IE10+ : (has Blob, but not a[download] or URL) return navigator.msSaveBlob(blob, fileName); } 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===toString ){ try{ return saver( "data:" + mimeType + ";base64," + self.btoa(blob) ); }catch(y){ return saver( "data:" + mimeType + "," + encodeURIComponent(blob) ); } } // Blob but not URL support: reader=new FileReader(); reader.onload=function(e){ saver(this.result); }; reader.readAsDataURL(blob); } return true; }; /* end download() */ }));
js文件下载插件介绍和使用方法 download.js