JavaScript: get a random number from a specific range

random.js

/**
 * Get a random floating point number between `min` and `max`.
 * 
 * @param {number} min - min number
 * @param {number} max - max number
 * @return {number} a random floating point number
 */
function getRandomFloat(min, max) {
  return Math.random() * (max - min) + min;
}

/**
 * Get a random integer between `min` and `max`.
 * 
 * @param {number} min - min number
 * @param {number} max - max number
 * @return {number} a random integer
 */
function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1) + min);
}

/**
 * Get a random boolean value.
 * 
 * @return {boolean} a random true/false
 */
function getRandomBool() {
  return Math.random() >= 0.5;
}

Is the range inclusive on both ends? If I call getRandomInt(1, 5) are 1 and 5 BOTH possible returns?

@kerimdzhanov, but if the random be 1, this will not be wrong... = (

getRandomInt( 1,5 );
Math.floor(Math.random() * ( 5 - 1 + 1) + 1);
Math.floor(Math.random() * ( 5 ) + 1);
Math.floor( 1 * ( 5 ) + 1);
6;

My suggestion is limit the max. What do you think?

function getRandomInt(min, max) { return Math.min( max, Math.floor(Math.random() * (max - min + 1) + min) ); }

return (Math.random() * (max - min + 1) + min) | 0; would be faster if you are sensitive with code performance.

but now, in new chrome, there are no difference.

@AndrePessoa
Math.random() never gives 1, so there's no need to use Math.min() or @gonejack solution.

What I cannot seem to compute in my head is the "+min" at the end. I understand (max - min + 1) for inclusivity of the full range, but am at a lost to why you need the +min. What am I not getting?

function getRandomIntInclusive(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min;

@hackyourcraft without "+min" the range would start at 0.

You are best :)

When the parameter is only one. The "min" becomes the max and "min" is 0

random(min, max) {
    return (Math.random() * ((max ? max : min) - (max ? min : 0) + 1) + (max ? min : 0)) | 0;
}

Thank you!

I need to generate random numbers using javascript could you plz review?

Here are the same functions using ES6 syntax:

/**
 * Get a random floating point number between `min` and `max`.
 * 
 * @param {number} min - min number
 * @param {number} max - max number
 * @return {number} a random floating point number
 */
let randomFloat = (min, max) => Math.random() * (max - min) + min;

/**
 * Get a random integer between `min` and `max`.
 * 
 * @param {number} min - min number
 * @param {number} max - max number
 * @return {number} a random integer
 */
let randomInt = (min, max) => Math.floor(Math.random() * (max - min + 1) + min);

/**
 * Get a random boolean value.
 * 
 * @return {boolean} a random true/false
 */
let randomBool = () => Math.random() >= 0.5;

this might be late, but hopefully it helps someone else in the future.

Math.floor(Math.random() * max) + min;

between 4,6
Math.floor(Math.random() * 6) + 4;

Thanks

If it's okay with you, I'm going to use the code of random.js in a javascript extension I am working on (masmas.js)

thank you a lot

One-liner versions for anyone that's interested:

const getRandomFloat = (min, max) => Math.random() * (max - min) + min;
const getRandomInt = (min, max) => Math.floor(Math.random() * (max - min + 1) + min);
const getRandomBool = () => Math.random() >= 0.5;

Very usefull, thank you ...

One modification could be done with ES6 default parameters to allow it to take either one or two args.

function random(n, b = 0) {
    return Math.random() * (b-n) + n;
}

I want to print random number between 70 t0 100..

I want to print random number between 70 t0 100..

const number = getRandomInt(70, 100);

I want to print random number between 70 t0 100..

const number = getRandomInt(70, 100);

that's not working ... what is getRandomInt? there is no any predefined function of getRandomInt.. i tried Math.floor(Math.random*100);
but that wat i received 1 to 100 but I just need 70 to 100..

One-liner versions for anyone that's interested:

const getRandomFloat = (min, max) => Math.random() * (max - min) + min;
const getRandomInt = (min, max) => Math.floor(Math.random() * (max - min + 1) + min);
const getRandomBool = () => Math.random() >= 0.5;

can you expand this so we can easily understand line liner short code and long code like 1 vs 2

Really helpful, thanks!

I know this isn't recent but any tips on actually getting random numbers when a button calls this function often? I was using this to get some random results and the page displays repeats even after refreshing and reloading everything.

Thanks, I needed it

Random boolean method can also be implemented so:

function getRandomBool() {
  return !!Math.round(Math.random());
}

Thanks dude, its work on my machine