findTwitterIdsOnTwitterPage.js

        /*------------------------get Twitter Ids on page ---------------------
          
         |  Find twitter IDs of people on page(intended for blocking multiple
            users) bookmarklet inspired by @mariotaku 's wtb 
            
            
         |  Author: Hong Lin <plantvsbird@gmail.com>
            License: MIT
            
         |  See comments below for usage thx. 
         
         |  https://gist.github.com/plantvsbirds/ff8829a247d7fd522405
            
         *-------------------------------------------------------------------*/
(function (window, $) {
  if (location.href.indexOf('twitter.com') < 0) {
    alert('Please run this on twitter page, thx')
    return
  }
  anchors = $('a[data-mentioned-user-id],a[data-user-id]')
  map = {}
  anchors.each(function () {
    elem = $(this)
    link = elem.attr('href')
    name = elem.find('b').text() || link.slice(1, link.length - 1)
    id = elem.attr('data-mentioned-user-id') || elem.attr('data-user-id')
    if (id == '0')
      id = 'Visit profile page and run again please. <a href="' + link + '">Click Here</a>'
    map[id] = name
  })
  promptText = [
    '',
    'All Twitter accounts found on page',
    ''
  ]

  ansInLines = Object.keys(map).map(function (k) {
    return '[' + map[k] + '] : '+ k +' '
  })
  finalText = promptText
    .concat(ansInLines)
    .concat(promptText)
    .concat(['<button type="button" onclick="window.open(\'\', \'_self\', \'\'); window.close();">Close</button>'])
    .join('<br>')
  alertWindow = window.open()
  alertWindow.document.write(finalText)
  if(!alertWindow || alertWindow.closed || typeof alertWindow.closed=='undefined')  {
    alert('Disable your popup blocking plz')
  }
})(window, jQuery)

Use this as bookmarklet.
Ctrl + D to add this page. Then click EDIT, change the address to following
(just minified version. no harmful stuff fucking with you)

javascript:!function(e,t){return location.href.indexOf("twitter.com")<0?void alert("Please run this on twitter page, thx"):(anchors=t("a[data-mentioned-user-id],a[data-user-id]"),map={},anchors.each(function(){elem=t(this),link=elem.attr("href"),name=elem.find("b").text()||link.slice(1,link.length-1),id=elem.attr("data-mentioned-user-id")||elem.attr("data-user-id"),"0"==id&&(id='Visit profile page and run again please. <a href="'+link+'">Click Here</a>'),map[id]=name}),promptText=["","All Twitter accounts found on page",""],ansInLines=Object.keys(map).map(function(e){return"["+map[e]+"] : "+e+" "}),finalText=promptText.concat(ansInLines).concat(promptText).concat(["<button type=\"button\" onclick=\"window.open('', '_self', ''); window.close();\">Close</button>"]).join("<br>"),alertWindow=e.open(),alertWindow.document.write(finalText),void((!alertWindow||alertWindow.closed||"undefined"==typeof alertWindow.closed)&&alert("Disable your popup blocking plz")))}(window,jQuery);

When on twitter page, just click the bookmark you added to run script.