example.js

var browserSync = require("browser-sync");

browserSync.use({
    plugin: function () { /* noop */},
    hooks: {
        'client:js': require("fs").readFileSync("./reloader.js", "utf-8") // Link to your file
    }
});

browserSync({
    server: "./app",
    files: [
        "css/*.css",
    ],
    open: false
});

reloader.js

/**
 * Reload plugin example
 */
(function ($window, $document, bs) {

    var socket = bs.socket;
    var canReload = false;

    socket.on("connection", function (client) {
        if (canReload) {
            canReload = false;
            window.location.reload();
        }
    });
    socket.on("disconnect", function (client) {
        canReload = true;
    });
    
})(window, document, ___browserSync___);