save-download-blob.js

/*global Blob, atob, confirm, location, FileReader*/
// download.js v4.0, by dandavis 2008-2015. [CCBY2] 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
// https://github.com/rndme/download

module.exports = function download (data, strFileName, strMimeType) {
  var self = window // this script is only for browsers anyway...
  var u = 'application/octet-stream' // this default mime also triggers iframe downloads
  var m = strMimeType || u
  var x = data
  var D = document
  var a = D.createElement('a')
  var z = function (a) { return String(a) }
  var B = (self.Blob || self.MozBlob || self.WebKitBlob || z)
  B = B.call ? B.bind(self) : Blob
  var fn = strFileName || 'download'
  var blob
  var fr

  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?

  blob = x instanceof B
    ? x
    : new B([x], { type: m })

  function d2b (u) {
    var p = u.split(/[:,]/)
    var t = p[1]
    var dec = p[2] === 'base64' ? atob : decodeURIComponent
    var bin = dec(p.pop())
    var mx = bin.length
    var i = 0
    var 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
    }

    if (typeof safari !== 'undefined') { // handle non-a[download] safari as best we can:
      url = 'data:' + url.replace(/^data:([\w\/\-\+]+)/, u)
      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 = 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
}