嘿！ 为什么我的 Javascript 代码不起作用

Question

I tried to create a function in Javascript that will give a random integer between two integers (including both). But, unfortunately this is not including the first integer. The code is as follows:

const randomEjector = (num1,num2) => {return Math.ceil(Math.random() * (num2 - num1)) + num1}

I am considering the analogy of inequality.
++ Let's consider, ( Math.random() will output a no. between 0( including ) and 1( excluding )).
Let's say x = Math.random() , then x∈[0,1)
So, 0 ≤ x < 1
0 * (num2-num1) ≤ x * (num2-num1) < 1 * (num2-num1)
Again, x*(num2-num1)∈[0,1*(num2-num1))
Now opening Math.ceil() part:
But, Math.ceil() is like greatest integer function :
So, for (0,1] it will return 1 .
for 0 => 0
and for interval ((num2-num1)-1,(num2-num1)) ,it will return (num2-num1) .
So, After Math.ceil() is executed, we should be left with an interval [0,(num2-num1)] .
Now, x*num2-num1 ∈ [0,(num2-num1)]
Finally, let y = x*(num2-num1)
So, 0 ≤ y ≤ (num2-num1)
So, 0 + num1 ≤ y + num1 ≤ (num2-num1) + num1
Which will give num1 ≤ y + num1 ≤ num2
Let, z = y + num1
So, z ∈ [num1,num2]
Then, why my function is excluding 1st term and making it like (num1,num2]?
Where's the problem?
For instance for console.log(randomEjector(3,4)) , it will always give 4 and never 3.

Answer 1

It's unspeakably unlikely that Math.random() will ever return exactly 0, so Math.ceil(Math.random()) will unspeakably likely always return 1.

In other words, randomEjector(3,4) will, once in a very, very blue moon, give you 3.

Answer 2

It returns 4 because you are always ceiling the result, if you want it to return 4 then you need to floor the result.