benhowdle89 - 2 years ago 53
Javascript Question

# Generating unique random numbers (integers) between 0 and 'x'

I need to generate a set of unique (no duplicate) integers, and between 0 and a given number.

That is:

``````var limit = 10;
var amount = 3;
``````

How can I use Javascript to generate 3 unique numbers between 1 and 10?

Use the basic `Math` methods:

• `Math.random()` returns a random number between 0 and 1 (including 0, excluding 1).
• Multiply this number by the highest desired number (eg 10)
• Round this number

``````Math.round(Math.random()*10) + 1
``````

Example:

``````//Example, including customisable intervals [lower_bound, upper_bound)
var limit = 10,
amount = 3,
lower_bound = 1,
upper_bound = 10,
unique_random_numbers = [];

if (amount > limit) limit = amount; //Infinite loop if you want more unique
//Natural numbers than existemt in a
// given range
while (unique_random_numbers.length < limit) {
var random_number = Math.round(Math.random()*(upper_bound - lower_bound) + lower_bound);
if (unique_random_numbers.indexOf(random_number) == -1) {
// Yay! new random number
unique_random_numbers.push( random_number );
}
}
// unique_random_numbers is an array containing 3 unique numbers in the given range
``````
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