What does Math.random() do in this JavaScript snippet?

What does Math.random() do in this JavaScript snippet?

I'm watching this Google I/O presentation from 2011
https://www.youtube.com/watch?v=M3uWx-fhjUc
At minute 39:31, Michael shows the output of the closure compiler, which
looks like the code included below.
My question is what exactly is this code doing (how and why)
// Question #1 - floor & random? 2147483648?
Math.floor(Math.random() * 2147483648).toString(36);
var b = /&/g,
c = /</g,d=/>/g,
e = /\"/g,
f = /[&<>\"]/;
// Question #2 - Looks like sanitizing input... yes?
function g(a) {
a = String(a);
f.test(a) && (
a.indexOf("&") != -1 && (a = a.replace(b, "&amp;")),
a.indexOf("<") != -1 && (a = a.replace(c, "&lt;")),
a.indexOf(">") != -1 && (a = a.replace(d, "&gt;")),
a.indexOf('"') != -1 && (a = a.replace(e, "&quot;"))
);
return a;
};
// Question #3 - void 0 ???
var h = document.getElementById("submit-button"),
i,
j = {
label: void 0,
a: void 0
};
i = '<button title="' + g(j.a) + '"><span>' + g(j.label) +
"</span></button>";
h.innerHTML = i;