使用javascript访问文件是否安全？

Question

<input type="file" id="files" name="files[]" multiple />
<output id="list"></output>

<script>
  function handleFileSelect(evt) {
    var files = evt.target.files; // FileList object

    // files is a FileList of File objects. List some properties.
    var output = [];
    for (var i = 0, f; f = files[i]; i++) {
      output.push('<li><strong>', escape(f.name), '</strong> (', f.type || 'n/a', ') - ',
                  f.size, ' bytes, last modified: ',
                  f.lastModifiedDate ? f.lastModifiedDate.toLocaleDateString() : 'n/a',
                  '</li>');
    }
    document.getElementById('list').innerHTML = '<ul>' + output.join('') + '</ul>';
  }

  document.getElementById('files').addEventListener('change', handleFileSelect, false);
</script>

我要使用javascript阅读文件，但我不知道使用javascript访问文件是否安全。如果有人知道那么请帮助我...