title: "Upload" local file to localStorage (without server-interaction)
body: <p>I was about to ask 'How to "download" localStorage?' but fortunately found <a href="https://stackoverflow.com/questions/17836273/export-javascript-data-to-csv-file-without-server-interaction">this</a> and my original question was solved.</p>
  
  <p>Now then, how can I allow the user to "upload" a local file to localStorage or javascript in general? I'm not asking the way to access the local files in background which is clearly prohibited; I want the user to select their local file explicitly.</p>
  
  <p>For example, if the user has <code>save.json</code>:</p>
  
  <pre><code>{
      "hp": 32,
      "maxHp": 50,
      "mp": 11,
      "maxMp": 23
  }
  </code></pre>
  
  <p>How can I set this to localStorage by just asking the user to upload this file?</p>