How can I get selected text in pdf in Javascript?

Question

I\'m writing a Chrome Extention to manipulate pdf file so I want to get selected text in the pdf. How can I do that.

Some thing like that:

Answer 1

You can use the internal undocumented commands of the built-in PDF viewer.
To access it your content script should do it in page context:

function getPdfSelectedText() {
  return new Promise(resolve => {
    window.addEventListener('message', function onMessage(e) {
      if (e.origin === 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai' &&
          e.data && e.data.type === 'getSelectedTextReply') {
        window.removeEventListener('message', onMessage);
        resolve(e.data.selectedText);
      }
    });
    const script = document.createElement('script');
    document.documentElement.appendChild(script).text =
      "document.querySelector('embed').postMessage({type: 'getSelectedText'}, '*')";
    script.remove();
  });
}

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg === 'getPdfSelection') {
    getPdfSelectedText().then(sendResponse);
    return true;
  }
});