JavaScript | Random

Last Updated : 27 Mar, 2019

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 be scaled according to the desired range.

Syntax:

Math.random()

Example: This example uses Math.random() function to returns a random number.

<!DOCTYPE html> 
<html> 
  
<body> 
    <h2>Math.random()</h2> 
  
    <p> 
        Math.random() returns a random 
        number between 0 and 1 
    </p> 
  
    <p id="GFG"></p> 
      
    <!-- Script to use Math.random() function -->
    <script> 
        document.getElementById("GFG").innerHTML 
                = Math.random(); 
    </script> 
</body> 
  
</html>                     

Output:

Random Integers: The Math.random() method is used with Math.floor() function to return random integers.

Example:

<!DOCTYPE html> 
<html> 
  
<body> 
    <center> 
        <p> 
            Math.floor(Math.random() * 11) returns 
            a random integer between 0 and 10  
            (inclusive): 
        </p> 
              
        <p id="demo"></p> 
    </center> 
      
    <!-- Script to use Math.random() function 
    and Math.floor() function to return random 
    integer -->
    <script> 
        document.getElementById("demo").innerHTML = 
                    Math.floor(Math.random() * 11); 
    </script> 
</body> 
  
</html>                     

Output:

Proper Random Function: JavaScript function always returns a random number between min and max where min is inclusive and max may be inclusive or exclusive both.
Example:

<!DOCTYPE html> 
<html> 
  
<body> 
    <p> 
        When you click the button it will 
        give a random value between 0 and 
        9 both inclusive: 
    </p> 
          
    <button onclick="document.getElementById('GFG').innerHTML =  
                getRndInteger(0, 10)">Try it</button> 
                      
    <p id="GFG"></p> 
      
    <!-- Script to return random number between 
        0 and 10 -->
    <script> 
        function getRndInteger(min, max) { 
            return Math.floor(Math.random() * (max - min)) + min; 
        } 
    </script> 
</body> 
  
</html>                     

Output on first click:

Output on second click:

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