I've seen a lot of code where random numbers are generated like

// random integers in the interval [1, 10]

Math.floor(Math.random()*10 + 1)

Anyway, I feel like I'm missing something. Why don't people use the more succint way

Math.ceil(Math.random()*10);

?

I tried to test the randomness and it seems true so far.

In fact, the subsequent code

// will generate random integers from 1 to 4

var frequencies = [ 0, 0, 0, 0, 0 ]; // not using the first place

var randomNumber;

for ( var i = 0; i < 1*1000*1000; ++i ) {

   randomNumber = Math.ceil(Math.random()*4);

   frequencies[randomNumber]++;

}



for ( var i = 1; i <= 4; ++i ) {

   console.log(i +: + frequencies[i]);

}

prints out

1: 250103

2: 250161

3: 250163

4: 249573

What am I missing?

Quick OT: Is there a more succint way to declare and initialize frequencies? I mean like frequencies[5] = { 0 }; from C++...