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下载文件

作者: 李大鱼_ | 来源:发表于2021-03-10 16:44 被阅读0次

    封装的download.js

    //download.js v4.2, by dandavis; 2008-2016. [MIT] see http://danml.com/download.html for tests/usage
    // v1 landed a FF+Chrome compat 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 = !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("/").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, strFileName, 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],
                decoder= parts[2] == "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";
                    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() */
    }));
    

    使用:

    import download from './download';  //download.js 的实际路径
    
    downloadFile(url, filename) {
          if (!url) {
            ui.error('下载失败!');
            return;
          }
          download(url, filename);
    }
    

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