Break on alert()

break-on-alert.user.js

// ==UserScript==
// @name         Break on alert()
// @namespace    https://gist.github.com/r-k-b/
// @version      1.0.0
// @description  Where is that damned `alert()` called from? This drops the trace in the console. If the Dev Tools are open, it'll also pause execution.
// @author       Robert K. Bell
// @homepage     https://gist.github.com/r-k-b/f804b3c2e7f6800f4c326ec11a190b8d
// @downloadURL  https://gist.github.com/r-k-b/f804b3c2e7f6800f4c326ec11a190b8d/raw/break-on-alert.user.js
// @match        *://*/*
// @grant        none
// @run-at       document-start
// ==/UserScript==

/* jshint esnext: true */

(() => {
    'use strict';

    const oldAlert = alert;
    alert = function() {
        console.trace('here\'s the trace for an `alert()`, called with args:', arguments);
        debugger;
        oldAlert(...arguments);
    };
})();