How to get random number in JavaScript

 Generating a Random Number

In JavaScript, you can get random number using Math.random( ) function. This function return a floating- point number from 0 (inclusive) to 1(exclusive).

JavaScript:

var randomNumber = Math.random();

console.log(randomNumber); //0.3039685388621798

This method generate a float number from 0 to 1, but we want a integer value so we use another method Math.floor( ) which convert float number into integer.

Math.floor( ) return a rounded down integer

JavaScript:

var randomNumber = Math.random() // 0.25428721717092606

randomNumber = randomNumber * 10; // 2.5428721717092606

randomNumber = Math.floor(randomNumber)

console.log(randomNumber); // 2

above method return a value from 0 to 9 but it did not return value of 10 (inclusive). if you want to value from 0 to 10. so you should  Math.random() * 11 multiply by 11 and if you want to 1 to 10 so you have add 1 after  Math.floor(Math.random() * 11) + 1; 

JavaScript:

var randomNumber = Math.floor(Math.random() * 11) + 1;

console.log(randomNumber);

Get a random number from a specific range

to get random number from specific range, let's say from 5 to 10( both inclusive ), you should apply following code.

JavaScript:

let minVal = 5;

let maxVal = 10 + 1; // Adding 1 to include the maxVal

randomNumber = Math.floor(Math.random() * (maxVal - minVal ) ) + minVal;

console.log(randomNumber);

Math.random() generate a random number with uniform distribution. 

In this method, Math.floor(Math.random() return a random number from 0 to 1, and then multiply by difference between maxValand minVal value . By flooring the result and adding by min . we obtain a random integer from 5 to 10.