error in custom.js – syntax error, unrecognized expression

I am having a javascript error triggered by a line of code in custom.js. This is stopping all animations from working properly (slides, lazy loading images etc).

Can anyone tell me how I can find out who is responsible for this custom.js file, so I can contact the developer for support? Is it wordpress (doubt it, somehow), is it my Divi theme (probably although I hope not – I have to pay to get support!!!) or a plugin?

web-site is engagelearnshare.com (please don’t laugh – it’s my first attempt!!)