js实现点击浏览器自动下载

记录一下用纯js实现各种浏览器自动下载的功能。
兼容IE。

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downloadDocument("YOUR DOCUMENT");

function downloadDocument(pdfType) {
  // your defination of file url and file name
  let fileUrl = documentInfo[pdfType]["url"];
  let fileName = `${documentInfo[pdfType]["name"]}.pdf`;

  const oReq = new XMLHttpRequest();
  oReq.open("GET", fileUrl, true);
  oReq.responseType = "blob";
  oReq.onload = function () {
    const fileBlob = new Blob([oReq.response], {
      // or other type
      type: "application/pdf",
    });
    saveAs(fileBlob, fileName);
  };
  oReq.send();
}

function saveAs(blob, filename) {
  const URL = window.URL || window.webkitURL
  const type = blob.type
  const force_saveable_type = 'application/octet-stream'
  const slice = blob.slice || blob.webkitSlice || blob.mozSlice
  blob = slice.call(blob, 0, blob.size, force_saveable_type)
  const url = URL.createObjectURL(blob)
  const save_link = document.createElementNS(
    "http://www.w3.org/1999/xhtml",
    "a"
  );
  save_link.href = url;
  save_link.download = filename;

  const event = new MouseEvent("click", {
    bubbles: true,
    cancelable: true,
    view: window,
  });
  save_link.dispatchEvent(event);
  URL.revokeObjectURL(url);
}