Jump to content
  • Announcements

    • boen_robot

      Guidelines and Netiquette   03/28/2017

      Posting Problems:   Having problems posting your topic? Read through this: To join, you agree to our terms and conditions and fill out and submit a registration form. An activation email will be sent to your email adress, so you'll need to verify your account. After that the account has to be validated by one of the moderators. This will mean that it can take up to a day to be activated. A couple of things to remember to ensure approval: Don't use an email address in one of those $2 four character .com domains eg. xyds.com. These will be deleted and the domain added to the banned list. Don't use an email address that is within a domain with a bad reputation for spam. A Google search is run on every email address and email domain. Don't sign up with an email address that doesn't exist, doesn't work or requires the sender to answer a quiz before their email can get to you. Put your country and or state and city in the signup form. Blank forms will go to the botton of the "to do" list. And make sure that your email address and your country match, saying you're from Alabama and using a .ru email address is not going to get you activated. After a membership is activated the first few posts will be monitored. Posting spam or unapproved topics described in the agreement results in an immediate ban. The email provider and the IP addresses associated with the account will be banned and all posts will be deleted. These strict measures have been deemed necessary to hinder spam. Sorry for any inconvenience this causes, but it's not liable to change. If, after reading this, you still can't post and don't understand why, contact one of the Moderators listed here.   Topic Guidelines   Including the following information can expedite an accurate response from board members: Must be a Specific Problem or Question related to web design and development Include Code in Question (wrap with   for small blocks of code and for longer blocks   ) Include Code Author Include Extra Notes/Modifications/Attempts Include web link to page/file when possible Content Guidelines   You may not post, upload, link to, or email any Content that contains, promotes, gives instruction about, or provides prohibited Content. Prohibited Content includes any Content that breaks any local, state, county, national or international law. Prohibited Content also includes: No direct or indirect advertising or websites, forums, products, services No hijacking of posts (do not post your question in someone elses) Content that infringes upon any rights [ex. MP3s and ROMs] (including, but not limited to, copyrights and trademarks) Abusive, threatening, defamatory, racist, or obscene Viruses or any other harmful computer software False Information or libel Spam, chain letters, or Pyramid schemes Gambling or Illicit drugs Terrorism Hacking or cheating for internet/online games Warez, Roms, CD-Keys, Cracks, Passwords, or Serial Numbers Pornography, nudity, or sexual material of any kind Excessive profanity Invasive of privacy or impersonation of any person/entity Hacking materials or information Posting Tips   There are more BBcodes than there are buttons for on the reply menu. To get the full list, click "BB Code Help" underneath the clickable smilie face menu. Use   for small snippets of code Use   for lengthy snippets of code Use   if your snippet is HTML (optional) Use   if your snippet is SQL (optional) Rules of Conduct   Be nice. There's no need for calling someone stupid if they ask an 'easy' question. Keep your avatars and signatures absolutely child friendly. We have a younger audience on this forum. Keep your language appropriate for the same reason above. Do not PM moderators for help on the forum. Post on the topic, or create a new one.   Spam:   Recently, as you have all without doubt noticed, we have had lots of spam and advertisement on the forum. Therefore, we'd like to alert you as to what to do when you have found any of the aforementioned annoying messages: it. Immediately. Give a clear reason, please, if the advertising is not evident. DO NOT POST! Report, let the post stay as is, and we will get to it, meanwhile if you continue to post as normal in the other threads, it won't be on the top so long. Refrain from PMing the member. This won't help at all, as they are most likely spambots anyway. Thank you.       Images in signatures:   After thinking of users on dial-up, we have decided to enforce the following rules regarding signatures. Please pay heed to them. Respecting these rules is respecting the members on this forum with dial-up. Signature rules: No animated images AT ALL. No matter the amount of animation. Maximum image widthxheight: 300x150 Maximum image (file) size: 15kb Use calm colors. Do not use highly contrasting images in your signature, as this can get really annoying when seeing several posts from one member in the same thread. The same prohibited content goes for images as for posts. Lastly, use common sense. No lengthy signatures please. Save us some scrolling. Thank you.       Links in signatures:   Please understand that w3schools.com only exists because of voluntary work and is barely supported by the advertising littered throughout the tutorials and the forum. So, please, stop advertising other sites. DO not post links that drive traffic away from the w3schools domain - especially to a site that offers similar if not identical information. Please help support the site by keeping individuals on it. Thank you. Here are some guidelines as to what you can put in your signature: w3schools links --> allowed w3.org links --> allowed browser links --> allowed html editor links --> allowed personal sites --> allowed tutorial sites competing with w3schools --> NOT allowed sites completely irrelevant to webprogramming and this forum --> NOT allowed   Thanks for understanding, and for taking the time to read this. ~W3Schools Modstaff~
hisoka

javascript code does not show result

Recommended Posts

hisoka    2

I have this javascript code and when I run it it does not print the result :
 

function isprime(n)
{

  if (n<2)
  {
   return false;
  }
 
  var q = Math.floor(Math.sqrt( n));
   
  for( i = 2 ; i<= q ; i++)
  {
    var result = n%i;
    
    if(result==0)
       
      
     {
      
     return false;
     
      }
    
   else
     
    {
     document.write(result);
    }
    
  }
 
}


var prime = isprime(100);

I do not know why ? any help on what is the problem is and how to solve it

Share this post


Link to post
Share on other sites
justsomeguy    939

That function isn't written very well, it doesn't even always return a value.  If you actually give it a prime number like 17 it doesn't return any value at all.  If a function is going to return a value, it should always return a value.  That function will never return true, how are you supposed to know if the number is prime or not?

Share this post


Link to post
Share on other sites
hisoka    2

That is why I put the code here and asked for help because I do not know how  that function will return a value , how it will print it in the computer screen so that I can see it . What to do so that the function is well written and how to do it !!

Quote

how are you supposed to know if the number is prime or not?

Generally I know that an integer is a prime if it is not divisible by any prime  less or equal to its square root hence we have in that code  the

  var q = Math.floor(Math.sqrt( n));

it gives the square root of a number combined with math.floor and the for loop it takes n % i which is n % all numbers that are less or equal to the square root of n and dismisses or ignore all the numbers that are divisible by n as they are not prime .

 

Moreover the role of the function is not to look if n is a prime or not otherwise to give all the primes between 2 and n

My problem is I cannot make it print the values . You wrote that is it not well written , it does not return a value ....... I know all that . So what do you suggest to make it well writeen , return a value and print it in the screen . What is the substitution ? any suggest from you on what to do ?

Share this post


Link to post
Share on other sites
justsomeguy    939

First, don't use document.write.  That might mess up testing.  Use console.log to print anything you want to the console, including debugging information.  If you want to test what the function does you can print that also, e.g.:

console.log("isprime(12):");
	console.log(isprime(12);
	console.log("isprime(17):");
	console.log(isprime(17);

Make sure that every path through the function will result in a return statement.  There is no "return true" in that function, that should be an indication that it's not doing what it's supposed to do.

Share this post


Link to post
Share on other sites
hisoka    2

I changed that code with another code :
 

function calculate(n)
{
for(i=0 ; i<=n ; i++)
{
 var isprime = false;
 for(j=2 ; j<=n ; j++)
 {
 if(i%j===0 && i!==j)
   {
    isprime = true;
   }
 }
 if(isprime===false)
   {
     console.log(i+"\n");
     
   }
 
}

}

console.log(calculate(17));

then it gives me :

1
 
2
 
3
 
5
 
7
 
11
 
13
 
17

undefined

I do not know why get undefined and how to correct the code so that I do not get undefined

Share this post


Link to post
Share on other sites
Ingolme    794

You got undefined because the function is not returning anything. The function must use the return statement.

  • Thanks 1

Share this post


Link to post
Share on other sites
dsonesuk    701

Just remove calculate(17) from console log(), it will add each value to console log without the need for return, also in Firefox the undefined shows for a Firefox file 'content.js' whixch is unrelated (check far right for filename causing undefined)

Share this post


Link to post
Share on other sites
dsonesuk    701

IF you still want to use console.() to call function with argument, store each value in variable and return THAT final result to console.log

            function calculate(n)
            {
                var results = "";
                for (i = 0; i <= n; i++)
                {
                    var isprime = false;
                    for (j = 2; j <= n; j++)
                    {
                        if (i % j === 0 && i !== j)
                        {
                            isprime = true;
                        }
                    }
                    if (isprime === false)
                    {
                        results += i + "\n";

                    }

                }
                return results;
            }

            console.log(calculate(25));

 

  • Thanks 1

Share this post


Link to post
Share on other sites
hisoka    2

Now I am trying to take a number as input in box and once I press ok all the primes that are less than it are generated I did like this :
 

function calculate(x)
{
var x = prompt("enter a number");

var results = "" ;
var y=parseInt(x);
  
 

for(i=0 ; i<n ; i++)
{
 var isprime = false;
 for(j=2 ; j<n ; j++)
 {
 if(i%j===0 && i!==j)
   {
    isprime = true;
   }
 }
 if(isprime===false)
   {
 
     results += i + "\n";
   }

}
return results; 
}

console.log(calculate(x));

but it gives no result . I know that something I added in the code is wrong but I do not know how to correct it .

Edited by hisoka

Share this post


Link to post
Share on other sites
dsonesuk    701

You are prompting for input within the scope of function to x variable, while calling the function with argument  outside the scope of function. It will never be able to know the variable x equals.

  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×