Introduced a simple way to save any bytes array as file from frontend

The usecase of this code is something like this: let image that user is making a protonmail or any another application that content inside frontend (=browser storage) some secret user's data that shouldn't be exposed to backend. Secret key for example or anything like that. This code allows to developer to save any `Array[Byte]` from frontend without hacks and question because creating a blob isn't clean. Unfortunately scalatags doesn't support `download` attribute and I need to make it by hand. I've opened a PR: com-lihaoyi/scalatags#212 to introduce it, but it might be a while until it is included to release.

Author: catap

core/.js/src/main/scala/io/udash/utils/FileDownload.scala

@@ -0,0 +1,23 @@
+package io.udash.utils
+
+import org.scalajs.dom.document
+import org.scalajs.dom.raw._
+import scalatags.JsDom.all._
+
+import scala.scalajs.js
+import js.JSConverters._
+import js.typedarray._
+
+object FileDownload {
+ def save(filename: String, bytes: Array[Byte], mimeType: String = "application/octet-stream"): Unit = {
+ val jsBytes = Array[js.Any](bytes.toTypedArray).toJSArray
+ val blob = new Blob(jsBytes, BlobPropertyBag(mimeType))
+ val url = URL.createObjectURL(blob)
+ val download = attr("download")
+ val anchor = a(href := url, download := filename, style := "display: none")(filename).render
+ document.body.appendChild(anchor)
+ anchor.click()
+ document.body.removeChild(anchor)
+ URL.revokeObjectURL(url)
+ }
+}