JavaScript check if browser extension is installed for Chrome, Firefox and Opera

Question

I want to show custom bar ( notification like: Install our plugin. ) on our site if extension is not installed for Chrome, Firefox and Opera. None will b

Answer 1

If the extension is willing to cooperate, it could advertise its presence to the document easily. For example:

---

The extension could do

window.$$myExt = ...

Then you can detect the extension by

if(typeOf $$myExt !== 'undefined'){...

(or any variation thereof)

Obtaining the page window is somewhat tricky at least

---

The extension could do

document.body.classList.add("myExt-visited")

Then you could detect the extension by

if(document.body.classList.contains("myExt-visited")){...

---

The extension could do

document.body.innerHTML += "
..."
// or $('body').append("
...");

then you could detect the extension by

if(document.getElementByID("myExt-toolbar")){...
// or if($("#myExt-toolbar").length){...

---

alternatively, you could do

   ...

and the extension would do

var replacement = document.getElementByID("myExt-replacement");
replacement && replacement.remove();

---

or you could do

function onMyExtExists(){
  ...
}

and the extension would do

onMyExtExists && onMyExtExists();