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How to generate random number in given range using JavaScript?

  • Difficulty Level : Hard
  • Last Updated : 23 Apr, 2019

A number generated by a process, whose outcome is unpredictable is called Random Number. In JavaScript, this can be achieved by using Math.random() function. This article describes how to generate a random number using JavaScript.

Method 1: Using Math.random() function: The Math.random() function is used to return a floating-point pseudo-random number between range [0,1) , 0 (inclusive) and 1 (exclusive). This random number can then be scaled according to the desired range.

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Syntax:

Math.random();

Example 1: This example generate an integer random number between 1(min) and 5(max).






<script> 
  
// Function to generate random number 
function randomNumber(min, max) { 
    return Math.random() * (max - min) + min;
  
document.write("Random Number between 1 and 5: "
  
// Function call
document.write( randomNumber(1, 5) ); 
</script>                                  

Output:

Random Number between 1 and 5: 1.0573617826058959

Method 2: Using Math.floor() function: The Math.floor() function in JavaScript is used to round off the number passed as parameter to its nearest integer in Downward direction of rounding i.e towards the lesser value.

Syntax:

Math.floor(value)

Example 2: This example generate random integer number between 1(min) and 100(max).




<script> 
  
// Function to generate random number 
function randomNumber(min, max) { 
    return Math.floor(Math.random() * (max - min) + min);
  
document.write("Random Number between 1 and 100: "
  
// Function call
document.write( randomNumber(1, 100) ); 
</script>                                     

Output:

Random Number between 1 and 100: 87

Example 3: This example generate random whole number between 1(min) and 10(max) both inclusive.




<script> 
  
// Function to generate random number 
function randomNumber(min, max) { 
    min = Math.ceil(min);
    max = Math.floor(max);
    return Math.floor(Math.random() * (max - min + 1)) + min;
  
document.write("Random Number between 1 and 10: "
  
// Function call
document.write( randomNumber(1, 10) ); 
</script>                                

Output:

Random Number between 1 and 10: 3



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