Tamper Monkey no alerts script

no-alerts.js

// ==UserScript==
// @name         No Alerts
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function(window, document) {
    'use strict';
    window.alert = function(message) {

        var a = document.getElementById('tampermonkey-alert-modal') || makeNewAlert()
        a.innerText = JSON.stringify(message)
    }
    // Your code here...
    function makeNewAlert() {
        var div = document.createElement('div')
        div.style.position = 'fixed'
        div.style.left = 'calc(50% - 200px)'
        div.style.top = 'calc(50% - 200px)'
        div.style.width = '400px'
        div.style.height = '400px'
        div.style.backgroundColor = 'lightgray'
        div.style.padding = '14px'
        div.style.fontSize = '1.2em'
        div.onclick = function() {
            div.remove()
        }
        document.body.appendChild(div)
        return div
    }
})(window, document);