Is generating and concatenating 3 Math.random() values more random than 1 Math.random() value?

I need to generate unique id's for multiple sentences in a longer narrative (where multiple users can be performing the same action, at the same time, on different machines).

I considered doing new Date().getTime() (and perhaps concatenating a username) but as the id's were generated in a loop whilst iterating over the sentences, I found duplicates were created (as generation could occur at the same millisecond).

So I am currently playing around with:

var random1 = Math.floor((Math.random() * 10000) + 1).toString(36);
var random2 = Math.floor((Math.random() * 10000) + 1);
var random3 = Math.floor((Math.random() * 10000) + 1);
var id = random1 + random2 + random3;
// generates things like:  
// 1h754278042
// 58o83798349
// 3ls28055962

It occurred to me though (admittedly, as someone who has not pondered unique/random/crypto issues much), that perhaps joining three random numbers isn't any more random that one random number?

Is generating and concatenating 3 Math.random() values more random than 1 Math.random() value?

This answer (http://ift.tt/29hEPSU) states:

If the random generator really produces random data then it will not matter.

But I'm not sure how that applies to the usage of Math.random().

Edit:

Scenario is client side on web and not for security, just to ensure that each sentence has a unique id in the database.