web下载

/**
 * 下载文件
 * @params data:文件blob
 * @params strFileName为文件名
 */
export 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("/").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
    }

  }//end if dataURL passed?

  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)) {
      url=url.replace(/^data:([\w\/\-\\+]+)/, defaultMime);
      if(!window.open(url)){ // popup blocked, offer direct download:
        if(window.confirm("Displaying New Document\n\nUse Save As... to download, then click back to return to this page.")){ window.location.href=url; }
      }
      return true;
    }

    //do iframe dataURL download (old ch+FF):
    var f = document.createElement("iframe");
    document.body.appendChild(f);

    if(!winMode){ // 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() */