math floor math random javascript example

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MDN Web Docs

Math.random() - JavaScript | MDN

function getRandomInt(max) { return Math.floor(Math.random() * max); } console.log(getRandomInt(3)); // Expected output: 0, 1 or 2 console.log(getRandomInt(1)); // Expected output: 0 console.log(Math.random()); // Expected output: a number from 0 to <1 · js · Math.random() None.

stackoverflow.com › questions › 75869530 › why-do-we-use-math-floor-for-creating-random-numbers-vs-math-round-or-math

javascript - Why do we use Math.floor() for creating random numbers vs. Math.round() or Math.ceil() - Stack Overflow

discuss.codecademy.com › frequently asked questions › javascript faq

The numbers from Math.random() are in the range 0 (inclusive) to 1 (exclusive). That means you might get a 0, but you'll never get 1.

Thus that formula starts off with multiplying by an integer, which in your example will give a value from 0 (inclusive) up to 4 (exclusive). If you want random integers like 0, 1, 2, and 3, you have to use .floor() to get rid of any fractional part entirely. In other words, you might get 3.999, and you don't want a 4, so .floor() throws away the .999 and you're left with 3.

Now this presumes that what you want is what most people want, a random integer between a minimum value and a maximum value. Once you understand what Math.random() returns, you're free to generate integers however you want.

Codecademy Forums

How do `Math.random()` and `Math.floor()` work together? - JavaScript FAQ - Codecademy Forums

April 5, 2019 - I’m currently taking the web ... Math.floor part, can anyone help me? console.log(Math.random()*100); ( this is the first part) Math.floor(Math.random)() *: ( this is the second part) ......

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Math.floor and Math.random function - JavaScript

That i understood. I even got the answer using that method and using the following code: function randomWholeNum() { // Only change code below this line var x = Math.random()*10; var y = Math.floor(x); return y; } What I want to understand is why the first method doesn’t work.

LaunchCode

education.launchcode.org › intro-to-professional-web-dev › appendices › math-method-examples › random-examples.html

Math.random Examples — Introduction to Professional Web Development in JavaScript documentation

floor = 0, ceil = 1, round = 0 floor = 6, ceil = 7, round = 7 floor = 2, ceil = 3, round = 3 floor = 8, ceil = 9, round = 8 floor = 9, ceil = 10, round = 10 · After multiplying Math.random() by 10, applying the floor method gives numbers between 0 and 9. Using the ceil method shifts the range ...

Medium

medium.com › @sanchit0496 › use-of-math-floor-math-random-num-in-javascript-practical-implementation-cc4cb54dafff

Use of Math.floor(Math.random()*num) in JavaScript — Practical Implementation | by Sanchit | Medium

March 26, 2019 - While making dynamic web projects, ... website. Such a functional code that is very often used in the projects is; Math.floor(Math.random()*num);...

stackoverflow.com › questions › 8002820 › why-would-i-combine-math-floor-with-math-random

javascript - Why would I combine Math.floor with Math.random? - Stack Overflow

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Math.random returns a floating-point number between 0 and 1.

Returns a floating-point, pseudo-random number in the range [0, 1) that is, from 0 (inclusive) up to but not including 1 (exclusive), which you can then scale to your desired range.

Multiplying this by n gives a floating point number between 0 (inclusive) and n (exclusive).

Math.floor is then used to convert this floating point number to an integer between 0 and n - 1 (inclusive).

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Why would anybody call Math.floor on a Math.random result?

In a nutshell, one calls Math.floor() when you want to truncate a decimal value to its nearest integer (by just dropping the decimal portion. So, 3.9 becomes 3, 2.1 becomes 2, etc... So, you would typically use that when you need an integer and you want the integer that is smaller than or equal to the decimal value. The math library also has Math.ceil() and Math.round(). Math.ceil() gets you the next larger integer, Math.round() rounds to the nearest integer going either up or down depending upon which is closer.

I've seen it used like: Math.floor(Math.random() * num);

Breaking Math.floor(Math.Random() * num) down into it's individual pieces and explaining each piece, you get this:

Math.random() gives you a random decimal number between 0 and 1, including 0, but not including 1. So, it might give you something like 0.38548569372.

Math.random() * num gives you a random decimal number between 0 and num, including 0, but not including num. So, if num was 10, it might give you 3.8548569372.

Math.floor(Math.random() * num)) gives you a random integer number between 0 and num, including 0, but not including num. So, it might give you 3.

Math.floor() truncates the decimal number to only the integer portion. A random integer is often used for getting a random value from an array (which needs to be an integer).

stackoverflow.com › questions › 75519675 › when-am-i-supposed-to-add-1-to-math-floor-math-random

javascript - When Am I supposed to add 1 to Math.floor Math random? - Stack Overflow

sitepoint.com › javascript

_"added 1 to left 10" no, you scale the random value over the range of possible output values.

You want a result in the range 10 - 20 inclusive, which is 11 possible integer values so you multiply the random value, x, (0 <= x < 1) by 11 to get a value, n, such that, 0 <= n < 11. By flooring the result you get an integer between 0 and 10 (inclusive). You then add 10 to this to get a value in the range 0 - 20.

Following that same logic for your second example Math.floor(Math.random() * 8) + 2;

Math.random() * 8 - results in a number x where 0 <= x < 8.
Math.floor(x) - gives an integer between 0 and 7, inclusive.
+ 2 - add an offset so the result is in the range 2 - 9.

To get a number between 2 and 8, you should change the initial 8 to 7 as you want a number in the range 2 - 8, which is one of 7 distinct integer values.

You shouldn't just add 1 without understanding the algorithm first. Once you do you can get a random integer between any 2 arbitrary numbers.

SitePoint

Math.random and Math.floor - JavaScript - SitePoint Forums | Web Development & Design Community

October 16, 2017 - Hello im new to javascript and i know what Math.floor(Math.random()) * 10; does, But what i don’t understand is why is math floor first and math random second? why dosent Math.random(Math.floor()) * 10; work?

DEV Community

dev.to › kanaga_vimala_66acce9cf6e › understanding-mathrandom-mathfloor-and-arrays-in-javascript-mkl

Understanding `Math.random()`, `Math.floor()`, and Arrays in JavaScript - DEV Community

June 1, 2025 - Math.random() → gives a number like 0.7382 · * 10 → scales it to 7.382 · Math.floor() → turns it into 7 · An array in JavaScript is a way to store a list of values. let fruits = ["apple", "banana", "cherry"]; console.log(fruits[0]); ...

reddit.com › r/webdev › why do we use math.floor() while generating random numbers in js?

r/webdev on Reddit: Why do we use Math.floor() while generating random numbers in JS?

October 15, 2020 -

why don't we use Math.ceil() instead of using the floor() function then adding 1, wouldn't it be much easier?

What would make it easier?

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Math.random() produce an number in the interval [0;1[Math.ceil(0) is still 0, not 1 To get an evenly distributed number accross the range, you would have to replace 0 after the ceiling. Math.floor(Math.random() * 10) + 1 Math.ceiling(Math.random() * 10) || 10 The first one is less confusing and "purely mathematical".

GeeksforGeeks

geeksforgeeks.org › javascript › javascript-math-random-method

JavaScript Math random() Method - GeeksforGeeks

July 15, 2024 - For getting a random integer between two values the Math.random() function can be executed in the following way: ... let min = 20; let max = 60; let random = Math.floor(Math.random() * (+max + 1 - +min)) + +min; console.log("Random Number Generated ...

stackoverflow.com › questions › 15830658 › random-number-math-floor-vs-math-ceil

javascript - Random Number, Math.floor(...) vs Math.ceil(...) - Stack Overflow