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JavaScript: get a random number from a specific range
/**
* 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;
}
@nullicorn
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nullicorn commented Jun 23, 2016

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

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ghost commented Apr 11, 2017

You are best :)

@nigeltiany
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nigeltiany commented May 31, 2017

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;
}

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ghost commented Aug 31, 2017

Thank you!

@Manjuanjanadri
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Manjuanjanadri commented Oct 12, 2017

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

@tejashah88
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tejashah88 commented Jan 30, 2018

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;

@msoliman85
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msoliman85 commented Apr 27, 2018

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;

@pen1120
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pen1120 commented Jul 20, 2018

Thanks

@N8python
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N8python commented Jan 21, 2019

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)

@aneurysmjs
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aneurysmjs commented Apr 11, 2019

thank you a lot

@Enijar
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Enijar commented Jun 24, 2019

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;

@ssugu42
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ssugu42 commented Jun 25, 2019

Very usefull, thank you ...

@maburdi94
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maburdi94 commented Jul 17, 2019

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;
}

@manubille
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manubille commented Oct 2, 2019

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

@kerimdzhanov
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Author

kerimdzhanov commented Oct 3, 2019

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

const number = getRandomInt(70, 100);

@manubille
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manubille commented Oct 11, 2019

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..

@manubille
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manubille commented Oct 11, 2019

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

@akj-maker
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akj-maker commented Jul 26, 2020

Really helpful, thanks!

@alh0059
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alh0059 commented Nov 23, 2020

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.

@Scratch-Guy
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Scratch-Guy commented May 27, 2021

Thanks, I needed it

@Sly-Little-Fox
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Sly-Little-Fox commented Jun 4, 2021

Random boolean method can also be implemented so:

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

@marvin46
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marvin46 commented Nov 5, 2021

Thanks dude, its work on my machine

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