Check a number is Prime or not using JavaScript

A prime number is a number that is divisible by 1 and itself only. First few prime numbers are: 2, 3, 5, 7, 11, 13, 17, …
A JavaScript uses the DOM model to check the input number is prime or not and display its corresponding alert message on the screen.

Examples:

Input : 4
Output : Not Prime

Input : 5
Output : Prime

Example 1: This example display the result by using alert function.

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<!DOCTYPE html>
<html>
  
<head>
    <title>
        Check a number is Prime or
        not using JavaScript
    </title>
      
    <script type="text/javascript">
      
        // Function to check prime number
        function p() {
              
            var n, i, flag = true;
              
            // Getting the value form text
            // field using DOM
            n = document.myform.n.value;
            n = parseInt(n)
            for(i = 2; i <= n - 1; i++)
                if (n % i == 0) {
                    flag = false;
                    break;
                }
                  
                // Check and display alert message
            if (flag == true)
                alert(n + " is prime");
            else
                alert(n + " is not prime");
        }
    </script>
</head>
  
<body>
    <center>
        <h1>GeeksforGeeks</h1>
          
        <h4>check number is prime or not</h4>
          
        <hr color="Green">
          
        <form name="myform">
            Enter the number:
            <input type="text" name=n value="">
              
            <br><br>
              
            <input type="button" value="Check" onClick="p()">
            <br>
        </form>
    </center>
</body>
  
</html>

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Output:


    

  • Before checking the number:
    

    • 

  • After checking the number:
    

    • 



Example 2: This example checks a given number is prime or not and display result on the console.











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<!DOCTYPE html> 


<html> 


  


<head> 


    <title> 


        Check a number is Prime or 


        not using JavaScript 


    </title> 


      


    <style> 


        body { 


            border:2px solid black; 


            width:400px; 


            height:150px; 


            text-align:center; 


        } 


        h1 { 


            color:green; 


        } 


    </style> 


      


    <script type="text/javascript"> 


      


        // Function to check for prime number 


        function checkPrime() { 


              


            var n, i, flag = true; 


              


            // Getting the value form the 


            // text field using DOM 


            n = document.myform.n.value; 


            n = parseInt(n) 


            for (i = 2; i <= n - 1; i++) 


                if (n % i == 0) { 


                    flag = false; 


                    break; 


                } 


                  


            // Check and display output 


            if (flag == true) 


                console.log(n + " is prime"); 


            else


                console.log(n + " is not prime"); 


        } 


    </script> 


</head> 


  


<body> 


        <h1>GeeksforGeeks</h1> 


        <h4>check number is prime or not</h4> 


      


        <form name="myform"> 


            Enter the number: 


            <input type="text" name=n value=""> 


            <input type="button" value="Check" onClick="checkPrime()"> 


            <br> 


        </form> 


    </center> 


</body> 


  


</html>                              



















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Output:


    

  • Before checking the number:
    

    • 

  • After checking the number:
    

    • 




          
          
          
          

            

    

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