Why an ad blocker and other privacy tools for your browser are essential

I did it in 46 lines, and isn't perfect, but the idea behind it is scary. With the javascript code below, after any webpage with this right above the </body> tag, I can track anyone on the website's clicks.

document.body.setAttribute("onmousedown", "whichElement(event)");
function whichElement(e) {
  var targ;
  if (!e) {
    var e = window.event;
  }
  if (e.target) {
    targ=e.target;
  } else if (e.srcElement) {
    targ=e.srcElement;
  }
  var tname;
  tname = targ.tagName;
  var aan;
  aan = tname.toLowerCase().substring(0, 1);
  var vowels = ['a','e','i','o','u'];
  if(vowels.includes(aan)){aan = 'an';} else {aan = 'a';}
  var tvalue;
  if(tname==="IMG"){
    tvalue = targ.src;
    console.log('You clicked on ' + aan + ' ' + tname + ' element: "' + tvalue + '".');
    sendTrackInfo('UserClick', tname, tvalue);
  } else if(tname!=="INPUT"&&tname!=="DIV"){
    tvalue = targ.innerText;
    if(!tvalue){tvalue = targ.title;}
    if(!tvalue){tvalue = "Unknown";}
    console.log('You clicked on ' + aan + ' ' + tname + ' element: "' + tvalue + '".');
    sendTrackInfo('UserClick', tname, tvalue);
  } else {
    console.log("You clicked on " + aan + " " + tname + " element.");
    sendTrackInfo('UserClick', tname, 'Login Form');
}
}
function sendTrackInfo(action, name, value){
  if(action&&name&&value){
  _paq.push(['trackEvent', action, name, value]);
  }
}
function sendUserInfo(){
  var username = "Unknown";
  if(document.getElementById("username") !== "undefined"){username = document.getElementById("username").textContent;}
  if(ncuser != "Unknown"){
    _paq.push(["setCustomVariable", 1, "User", username, "visit"]);
    console.log('"'+ncuser+'"');
  }
}

Necessary tools

• uBlock Origin - "NOT an 'ad blocker': it is a wide-spectrum blocker -- which happens to be able to function as a mere 'ad blocker'. The default behavior of uBlock Origin when newly installed is to block ads, trackers and malware sites -- through EasyList, EasyPrivacy, Peter Lowe’s ad/tracking/malware servers, various lists of malware sites, and uBlock Origin's own filter lists."
• HTTPS Everywhere - "a Firefox, Chrome, and Opera extension that encrypts your communications with many major websites, making your browsing more secure."
• Privacy Badger - "automatically learns to block invisible trackers."

Optional tools

• NoScript - turn off javascript completely or only allow the most trusted javascript sources.

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