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Generate random numbers in JavaScript by Cules Coding

Generate random numbers in JavaScript

In this blog, you will learn how to generate random numbers in javascript.

There is no straightforward way to generate a random number. You have to use a little trick.

Math.random function gives us a random number between 0 and 1.

const getRandomNum = () => {
    reutrn Math.random()
}


console.log(getRandomNum())
console.log(getRandomNum())
console.log(getRandomNum())
console.log(getRandomNum())


// output
// 0.4656524910632813
// 0.36946529666025185
// 0.93309610877532
// 0.6869999317373736

That's not what you want. You need an integer. To get an integer you need to multiply the random number with another number. And then you have to floor the value.

Get a random integer

const random = Math.random
const floor = Math.floor


const getRandomNum = () => {
    return floor(random() * 10)
}


setInterval(() => {
    const num = getRandomNum()


    console.log(num)
}, 500)


// Output:
// 2
// 5
// 1
// 9
// 1
// 7
// 6
// 0
// 7
// 3
// 4
// 8
// 2
// 2
// 4
// 5
// 5
// 0

By multiplying a number you have set an upper limit for the random number. We have floored the value because we don't want a floating-point number. Math.floor function gives us this

8.343487294263 --> 8
3.37294263     --> 3

Notice that we never get 10 as our random number. Because that is our limit. To include 10, just add 1 to the number.

Get a random integer in a range

Let's see how we can get a random number between 10 and 20

const random = Math.random
const floor = Math.floor


const getRandomNumInRange = (min, max) => {
    return floor(random() * (max - min + 1)) + min
}


setInterval(() => {
    const num = getRandomNumInRange(10, 20)


    console.log(num)
}, 500)


// output:
// 11
// 13
// 14
// 20
// 13
// 13
// 10
// 16
// 17
// 10
// 16

Explanation: Now we need something between two numbers. So, we generate random numbers up to the difference of our range. In our case, it will be 

difference = 10
random numbers = [
    2,3,4,6,10 ...
]

Then we add our minimum number with a random number. And that number definitely will be in the range.

You can write the code in one line.

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

That's how we get a random number in a range.

Shameless Plug

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That's it for this blog. I have tried to explain things simply. If you get stuck, you can ask me questions.

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