javascript - HTML Paste Clipboard Image to File Input

Question

Okay, here it goes. I have seen the great ways in which one can now paste images to WhatsApp web chats. Most examples use a canvas to capture the pasted clipboard image, how does one paste it to a File Input using only Ctrl + V anywhere on the page?

Here is the code I have for the input which automatically submits as soon as someone selected a file:

      <form id="new_document_attachment" method="post">
            <div class="actions"><input type="submit" name="commit" value="Submit" /></div>
                <input type="file" id="document_attachment_doc" />
      </form>
      <script>
          document.getElementById("document_attachment_doc").onchange = function() {
          document.getElementById("new_document_attachment").submit();
        };
      </script>

Answer 1

It's pretty straightforward. Just catch paste event on window object and put all the files you got from it to the <input> tag.

const form = document.getElementById("new_document_attachment");
const fileInput = document.getElementById("document_attachment_doc");

fileInput.addEventListener('change', () => {
  form.submit();
});

window.addEventListener('paste', e => {
  fileInput.files = e.clipboardData.files;
});

<form id="new_document_attachment" method="post">
  <div class="actions"><input type="submit" name="commit" value="Submit" /></div>
  <input type="file" id="document_attachment_doc" />
</form>