Error after Magento 2.3.0 - $.mage.isDevMode is not a function

Question

after upgrading from 2.2.6 to 2.3.0 I started to get this error, can't seem to find much info about this function.

I already cleared all cache folders, static files, regenerated them and nothing worked, all help is very much appreciated.

The log below is the only thing I got, generated on page load.

Using Magento 2.3.0 + PHP7.2 + MySql 5.3 + Nginx

VM142:5 Uncaught TypeError: $.mage.isDevMode is not a function
at $.(/anonymous function).(anonymous function)._create (eval at require.load (https://www.example.com/static/_cache/merged/0cea18d4374932b778cb47448cd0db91.min.js:182:216), <anonymous>:5:487)
at $.(/anonymous function).(anonymous function).eval [as _create] (eval at require.load (https://www.example.com/static/_cache/merged/0cea18d4374932b778cb47448cd0db91.min.js:182:216), <anonymous>:29:334)
at $.(/anonymous function).(anonymous function)._createWidget (eval at require.load (https://www.example.com/static/_cache/merged/0cea18d4374932b778cb47448cd0db91.min.js:182:216), <anonymous>:35:6)
at new $.(/anonymous function).(anonymous function) (eval at require.load (https://www.example.com/static/_cache/merged/0cea18d4374932b778cb47448cd0db91.min.js:182:216), <anonymous>:28:27)
at Object.$.(/anonymous function).(anonymous function) [as loaderAjax] (eval at require.load (https://www.example.com/static/_cache/merged/0cea18d4374932b778cb47448cd0db91.min.js:182:216), <anonymous>:27:241)
at eval (eval at require.load (0cea18d4374932b778cb47448cd0db91.min.js:182), <anonymous>:4:22)
at Object.execCb (0cea18d4374932b778cb47448cd0db91.min.js:112)
at Module.check (0cea18d4374932b778cb47448cd0db91.min.js:56)
at Module.enable (0cea18d4374932b778cb47448cd0db91.min.js:73)
at Module.init (0cea18d4374932b778cb47448cd0db91.min.js:54)

Answer 1

Never mind.

I had a meta name="description" tag lacking a double quote and the whole code was messed up.