Firefox – How to disable a specific JavaScript alert

firefoxjavascript

On an active website I go to, there is this javascript code that is displayed on every page.

<script type="text/javascript">
(function(){var d=document;var i=d.getElementsByTagName('iframe');if(google_ad_client!=null||(window.getComputedStyle?d.defaultView.getComputedStyle(i[i.length-1],null).getPropertyValue('display'):i[i.length-1].currentStyle['display'])=='none'){

alert('Adblock detected, please consider disabling it')

}})()
</script>

Is there any way that I could get my adblock — or any other type of plugin — to disable that specific code without disabling all javascript?

Best Answer

You can use the Greasemonkey add-on to rewrite the alert function:

// ==UserScript==
// @name        Catch JS Alert
// @namespace   http://igalvez.net
// @include     http://*
// @version     1
// @grant       none
// @run-at      document-start
// ==/UserScript==

window.alert = function(message) {
    if(message == 'Adblock detected, please consider disabling it') {
        console.log(message);
    } else {
        confirm(message);
    }
}

The way this works is as follows:

If the alert box's message matches "Adblock detected, please consider disabling it", then discard it to the JS console (it will not be displayed). Otherwise, display the alert box as a confirm box.

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