Require client-side

Question

Good morning.

In the company where I work, there is a kind of require client-side to import npm without it existing on the page. It is used to insert form scripts within the page. The code looks like this:

require(['jquery'], function () {
    //código com jquery
});

And within the scope of this function, jquery works even when there is no jquery on the page.

How is this done? I searched the internet for some server-side and client-side plugins, but none of them fit or works this way.