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Thread: window.prompt positioning help with prime function

  1. #1
    Join Date
    Nov 2012
    Posts
    3

    window.prompt positioning help with prime function

    Hey i was asked to write two programs. one that determines if an integer is a prime and another to state all the primes between two integers. I have written the first and it works perfectly fine (if not a little over complicated) but I'm having trouble with the second.
    I worked out the basic algorithm for it but i cant for the life of me work out how to incorporate two window.promt() into the code without messing it up. there meant for a low and high number for the user to input before receiving all the primes in between those numbers. Here is the basic code.

    <html>
    <body>
    <script language="javascript">

    l=1000;n=3;p=1;
    primes = new Array()
    primes[0]=2;
    while (n<=l){q=1;
    while (primes[q]<=Math.floor(Math.sqrt(n)) && n/primes[q]!=Math.round(n/primes[q])){q++;}
    if ((n-1)/1000==Math.round((n-1)/1000)){window.status="Numbers checked so far: "+(n-1);}
    if (n/primes[q]!=Math.round(n/primes[q])){primes[p]=n;p++;}
    n+=2;}
    document.write ("What follows next are prime numbers:<br>"+primes.join(", "));
    </script>
    </body>
    </html>

    I apologise for how messy it is. help would be appreciated I wont have any hair left to pull out soon

  2. #2
    Join Date
    Mar 2009
    Posts
    452
    why don't you use forms instead of window.prompt ?

  3. #3
    Join Date
    Oct 2010
    Location
    Versailles, France
    Posts
    1,276
    Do not use document.write ! You will be obliged to reload the page to rerun the script.
    Build your page with the following scheme
    Code:
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
    <html>
    <head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8">
    <meta name="generator" content="PSPad editor, www.pspad.com">
    <title>Prime numbers</title>
    <style type="text/css">
    input{width:40px;text-align:center}
    </style>
    </head>
    <body>
    <h1>Prime numbers</h1>
    
    <!-- a container for the first response -->
    <div id="rsp"></div>
    
    <!-- three inputs for entries and a button--> 
    <p>Displaying the primes between to intergers</p>
    <label>Min value <input id="mnv" type="text" value=""></label> 
    <label>Max value <input id="mxv" type="text" value=""></label> 
    <input type="button" value="Ok" onclick="calcPrim()">
    <!-- a new container for the second response -->
    <div id="rsq"></div>
    
    <!-- The script at the end of the body with a type instead of a language -->
    <script type="text/javascript">
    
    // Your script 
    l=1000;n=3;p=1;
    primes = new Array()
    primes[0]=2;
    while (n<=l){q=1;
    while (primes[q]<=Math.floor(Math.sqrt(n)) && n/primes[q]!=Math.round(n/primes[q])){q++;}
    if ((n-1)/1000==Math.round((n-1)/1000)){document.getElementById('rsp').innerHTML=<p>"Numbers checked so far: "+(n-1)+"</p>";}
    if (n/primes[q]!=Math.round(n/primes[q])){primes[p]=n;p++;}
    n+=2;}
    document.getElementById('rsp').innerHTML="What follows next are prime numbers:<br>"+primes.join(", ");
    
    // A function to read the values and to display the result
    function calcPrim(){
    	// the + sign convert the values to numbers
    	var min=+document.getElementById('mnv').value;
    	var max=+document.getElementById('mxv').value;
    	// A first test to improve (see isNaN) 
    	if (!min || !max) {alert("Please fill the min and max values !");return}
    	
    	// the calculation
    
    	// Dislaying the results
    	document.getElementById('rsq').innerHTML="<p><i>I have only to write the script to list the primes between "+min+" and "+max+".</i></p>";
    }
    </script>
    </script>
    </body>
    </html>

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