How FileReader.readAsText in HTML5 File API works?
<p>I wrote the following code to check whether the uploaded file exists or not using HTML5 file API.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
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<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;input type="file" id="myfile"&gt;
&lt;button type="button" onclick="addDoc()"&gt;Add Document&lt;/button&gt;
&lt;p id="DisplayText"&gt;&lt;/p&gt;</code></pre>
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<p>The following JavaScript code has been mapped to it is as follows:</p>

<pre><code>function addDoc() {
  var file=document.getElementById("myFile").files[0]; //for input type=file
  var reader=new FileReader();
  reader.onload = function(e) {}
  reader.readAsText(file);
  var error = reader.error;
  var texte=reader.result;
  document.getElementById("DisplayText").innerText=reader.result; /*&lt;p id="DisplayText&gt;*/
}
</code></pre>

<p>After browsing a file from local system I tried to delete the "browsed" document form the folder before clicking on <code>addDoc()</code>. After clicking the button I could still see <code>Filereader.result</code> is not null and could display all the content.</p>

<p>Can someone explain on how the <em>Filereader</em> works? Is it that the <em>FileReader</em> gets bound as soon as the file is browsed?</p>

<p>Also can we check whether the system <em>Readonly</em> Attribute with <em>FileReader</em> similar to Java <code>File.canread()</code>?</p>

<p>Could someone suggest on this? I have IE11 to test the code.</p>