Doubt about javascript modularization

Question

For a while I’ve seen in codes, including large Javascript libraries, more or less like this:

if (module.exports) {
    // faça algo
}

//#####
define({/* parametros */})

//#####
import algumacoisa from biblioteca

//#####
var foo = require('biblioteca')
// aqui, foo já é um objeto com metodos da biblioteca
foo.bar();

Anyway... I realized that all this is related to modularization. In Nodejs I know that this is used (I do not program in Node). What I don’t understand is this being used in front-end/client-side. Would this be promoted by some kind of transpiler? Or is it native? Because I tested many of these attributes in updated browsers and everything returned false or undefined. I even thought it was related to Ecmascript 6, but as I said, browsers don’t seem to support it natively.

Thank you.