Javascript simplifier?

I would like to eliminate functions that are unused or not related to the given context. Let's say we have:

function a(){ console.log('this is an unrelated function'); }
function b(){ console.log('world'); }
function c(){ console.log('hello' + b()); }
c();

Now a() is not used at all, and I don't need it, it just makes the script bigger. And this is actually the case with jQuery too. I'm not sure if I need that much code as jQuery has. I'm using jQuery only for highcharts and to select elements from the dom by id and class, but it would be really good to get rid of the unused functions because jQuery is just simply too big!

Are there online tools, services, functions/methods, apps that can do this minification?