Question

79

How to find prime numbers in entered number range

rated 0 times [ 85] [ 6] / answers: 1 / hits: 16626 / 11 Years ago, sat, february 15, 2014, 12:00:00

I'm just trying to find prime numbers of an entered range of numbers. I have no clue how to calculate finding primes. I need to add them to an array and output the array after. I put a placeholder for the calculation... I just can't seem to figure out how find the primes.

<!DOCTYPE html PUBLIC -//W3C//DTD HTML 4.01 Transitional//EN

  http://www.w3.org/TR/html4/loose.dtd>



<html>



    <head>

        <meta http-equiv=content-type content=text/html; charset=utf-8 />



        <title>LeapYears</title>



        <script type=text/javascript>

        /* <![CDATA[ */



        function calcPrimeNumber(){



                var beginNum = document.numbers.firstNum.value;

                var endNum = document.numbers.secondNum.value;

                var primeNumbs = new Array();





                var ctr = 0;

                while (beginNum <= endNum){ //throwaway

                    if ((beginNum % beginNum == 0) && (beginNum % 1 == 0)){

                        primeNumbs[ctr] = beginNum;

                        ++ctr;

                    }



                    ++beginNum;

                }



                if (primeNumbs == 0){

                    window.alert(There were no leap years within the range.);

                }



                else {

                    outputPrimeNums(primeNumbs);

                }



        }



        function outputPrimeNums(primes){

            document.write(<h2>Prime Numbers</h2>);

            for (i=0;i<primes.length;i++){

                    document.write(primes[i] + <br/>);

                }



        }





        /* ]]> */

        </script>





    </head>





    <body>

        <form name=numbers>



            Beginning Number: <input type=text name=firstNum /> End Number: <input type=text name=secondNum /> 

            <input type=button value=Find Prime Numbers onclick=calcPrimeNumber() />



        </form>



    </body>





</html>

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quinn

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answered 11 Years ago mariselas · Accepted Answer

try this full page of prime no example

<html>



    <head>

        <meta http-equiv=content-type content=text/html; charset=utf-8 />



        <title>LeapYears</title>



        <script type=text/javascript>

        /* <![CDATA[ */



        function calcPrimeNumber(){



                var beginNum = parseInt(document.numbers.firstNum.value);

                var endNum = parseInt(document.numbers.secondNum.value);

                var primeNumbs = new Array();





                var ctr = beginNum;

                while(ctr<=endNum)

                {

                    if(isPrime(ctr)==true)

                    {

                        primeNumbs[primeNumbs.length] = ctr;

                    }

                    ctr = ctr+1;



                }



                if (primeNumbs.length == 0){

                   document.getElementById('output_content').innerHTML = There were no prime no within the range.;

                }



                else {

                    outputPrimeNums(primeNumbs);

                }



        }



        function isPrime(num)

        {

            var flag = true;

            for(var i=2; i<=Math.ceil(num/2); i++)

            {

                if((num%i)==0)

                {

                    flag = false;

                    break;

                }

            }

            return flag;    

        }



        function outputPrimeNums(primes){

            var html = <h2>Prime Numbers</h2>;

            for (i=0;i<primes.length;i++){

                    html += primes[i] + <br/>;

                }

            document.getElementById('output_content').innerHTML = html;

        }





        /* ]]> */

        </script>





    </head>





    <body>

        <form name=numbers>



            Beginning Number: <input type=text name=firstNum /> End Number: <input type=text name=secondNum /> 

            <input type=button value=Find Prime Numbers onclick=calcPrimeNumber() />



        </form>

        <div id=output_content>

        </div>

    </body>





</html>