Random Number Generation Using Math.random() in JavaScript

In JavaScript, the Math.random() function is used to generate a pseudo-random floating-point number between 0 (inclusive) and 1 (exclusive). This means the generated number can be any value from 0 up to, but not including, 1.

Example 1: Print a random number

 

printRandomNumber.js

let randomNumber = Math.random();
console.log(`randomNumber : ${randomNumber}`);

 

Sample output on run 1

randomNumber : 0.1672875320265117

 

Sample output on run 2

randomNumber : 0.45151985242188997

 

Sample output on run 3

randomNumber : 0.5061797545590498

 

Generating Random Integers Within a Range

To generate a random integer within a specific range (say between min and max, inclusive), you can use the following function:

 

randNumberWithinRange.js

 

function getRandomInt(min, max) {
    min = Math.ceil(min); // Round up the min value to the nearest integer
    max = Math.floor(max); // Round down the max value to the nearest integer
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

console.log(`Random number between 5 and 10 ${getRandomInt(5, 10)}`);
console.log(`Random number between 5 and 11 ${getRandomInt(5, 11)}`);
console.log(`Random number between 5 and 12 ${getRandomInt(5, 12)}`);

 

Sample Output

Random number between 5 and 10 9
Random number between 5 and 11 11
Random number between 5 and 12 7

 

·      Math.random() generates a random floating-point number between 0 and 1.

·      This value is then multiplied by (max - min + 1), which represents the total number of possible integers between min and max, inclusive.

·      Math.floor() is used to round down the result to the nearest integer, ensuring it falls within the range.

·      Finally, min is added to shift the range from [0, (max - min)] to [min, max].

Generating Random Decimals Within a Range

To generate a random decimal number within a specific range, you can use the following function.

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

 

randDecimalWithinRange.js

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

console.log(`Random decimal between 5 and 10 : ${getRandomDecimal(5, 10)}`);
console.log(`Random decimal between 5 and 11 : ${getRandomDecimal(5, 11)}`);
console.log(`Random decimal between 5 and 12 : ${getRandomDecimal(5, 12)}`);

Output

Random decimal between 5 and 10 : 5.487781544915245
Random decimal between 5 and 11 : 6.190685752138041
Random decimal between 5 and 12 : 8.538375936112882

·      Math.random() generates a random floating-point number between 0 and 1.

·      This value is then multiplied by (max - min), which scales the random number to the desired range.

·      Finally, min is added to shift the range from [0, (max - min)] to [min, max).

 

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