web/web_switch_context_warning/static/src/js/switch_context_warning_worker.js

// Show a big banner in the top of the page if the context has been
// Changed in another tab or window (in the same browser)

var con = [];
var lastCtx = null;

addEventListener("connect", function (ee) {
    "use strict";

    var port = ee.ports[0];
    con.push(port);

    port.onmessage = function (e) {
        var newCtx = e.data;

        if (lastCtx && newCtx !== lastCtx) {
            con.forEach(function (eport) {
                eport.postMessage({type: "newCtx", "newCtx": newCtx, "lastCtx": lastCtx});
            });
        }
        lastCtx = newCtx;
    };
}, false);