Tampermonkey script

gistfile1.txt

// ==UserScript==
// @name         New Userscript
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://app.meiqia.com/chat/*
// @grant        none
// ==/UserScript==
/* jshint -W097 */
'use strict';

// Your code here...
var interval = setInterval(function () { 
    if (document.getElementsByClassName('info-panel').length)
    {
        console.log('trying');
        clearInterval(interval);
        document.getElementsByClassName('info-panel')[0].style.width = '400px';   
    }
}, 1000);