Javascript program to print prime numbers

Redu, I don't get "hate the sieving stuff"; in my mind it's all just tuning the algorithm to get the best performance including dividing the work so it can be efficiently multi-processed if that is an option. Redu, Your suggestion of putting my code s in a sandbox with commentary explaining how it works and why it's fast is a good one. This question is maxed out on answers and we are "well past our mandate" on sieving to billions when the question is to hundreds anyway.

I've already followed your lead and inserted live code into the other linked answer as per your comment. However, that answer is already getting too big and I don't want to add too much to it. I could add another answer there further expanding on that answer. I don't believe So allows making questions tutorials? Redu, in consideration of your proposed look at further optimizations to your SoS code, I don't see much point in that you will be working closer and closer to a SoE algorithm as I cover in my answer to a ComputerScience algorithm question other than if you want to take it further for your own better understanding.

In fact, your optimization to eliminate certain redundant culls is essentially just a relatively inefficient way of pre-culling to eliminate having to cull the factors of three, for which there are much more efficient ways to do it.

Redu, continued However, Even if you do even a greater level of pre-culling and more efficiently, you will still have more operations than the "odds-only" SoE due to sieving by all odd numbers rather than just by the odd primes, and you still haven't considered "maximum wheel factorization".

In other words, with reference to that other "algorithmic" answer, a fully optimized SoS becomes the SoE and you may as well use the Page Segmented SoE and be done with it Show 18 more comments.

A number is a prime if it is not divisible by other primes lower than the number in question. Vaibhav Vaibhav 1, 8 8 silver badges 13 13 bronze badges. Rahul Rahul 2 2 bronze badges. This answered worked for me and is so much simpler than the other answers I've seen. I'm not sure how j and i get to be different though as they both are rotating at the same time. Could you explain this, thanks? Luchian's answer gives you a link to the standard technique for finding primes.

Stephen C Stephen C k 90 90 gold badges silver badges bronze badges. Community Bot 1 1 1 silver badge. Naftali Naftali k 39 39 gold badges silver badges bronze badges. This is exactly the type of approach I was looking for.

Thanks for sharing. Here's a fast way to calculate primes in JavaScript, based on the previous prime value. Rinto Rinto 21 1 1 bronze badge. Sieve of Eratosthenes. Abdullah Aden Abdullah Aden 9 9 silver badges 13 13 bronze badges. When you do, please do not use tabs, they mess up formatting here, use only spaces please.

And your closing parenthesis is missing. I did it reading explanation of Sieve of Eratosthenes on wikipedia. You can turn it into one, if you change your inner for loop: change the starting point and the increment so that the test is guaranteed to be true always, by construction - so you can just omit the test. And that's what the proper s.

This will give 9,25 and more non-primes as prime numbers,please check — Vishal. Yes I had forgotten to increment the limit of search Math. Thanks for the test — kevin ternet.

Here's the very simple way to calculate primes between a given range 1 to limit. ManishS ManishS 2 2 gold badges 10 10 silver badges 21 21 bronze badges. Here's my stab at it. Aditya Singh Aditya Singh You can use this for any size of array of prime numbers.

Aslam Aslam 7, 3 3 gold badges 33 33 silver badges 48 48 bronze badges. We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

Why try deleting by 4 and 6,8,10,12 if we've already tried deleting by 2? Why try deleting by 9 if we've already tried deleting by 3? Why try deleting any odd number by 2 at all? Why try deleting any even number above 2 by anything at all? Will Ness Will Ness Why do we need to check till ? OmShankar IOW, this is an incremental sieve of Eratosthenes and m3 , m5 , m7 form an implicit priority queue of multiples of the primes 3, 5, and 7.

How would we extend it to , or 10,? Do we generate more m s, like m11, m13 etc. OmShankar yes, but -- to 10k you need primes below Either have a bona fide priority queue, or just use the regular sieve of E. Normally you'd go by segments - smaller arrays that fit in the memory cache, - and sieve them one after another.

Akash Jangra Akash Jangra 33 3 3 bronze badges. A version without any loop. Use this against any array you have. Please have a read of the formatting help page to improve the formatting in your answer, and also check out How do I write a good answer?

SJuan76 SJuan76 24k 6 6 gold badges 41 41 silver badges 80 80 bronze badges. It's actually between 2 and sqrt n. Yes, you are right. If a number bigger than sqrt n is a divider of n , it means that it is quotient is smaller than sqrt n so it would have been already found.

Naftali k 39 39 gold badges silver badges bronze badges. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked 1. See more linked questions. Next, create an else block and initiate the for loop inside it.

Inside the for loop, create another if block that checks whether the number value is divisible by the value of i and return false if it is. This is because the number must not be divisible by any other number except one and itself:.

The return keyword will stop the function execution and send the value false to the caller. You can store this value in a variable as follows:. This is why you should return true to let the function caller know that the number is a prime number.

Your checkPrime function is now done. You can test the code by calling the function multiple times with different numbers:. Check if a number is Positive, Negative, or Zero. Related Topics JavaScript while and do JavaScript Number. To understand this example, you should have the knowledge of the following JavaScript programming topics: JavaScript for loop JavaScript if All negative numbers are excluded because prime numbers are positive.

Numbers greater than 1 are tested using a for loop. Share on:. Did you find this article helpful? Sorry about that. How can we improve it? Leave this field blank. Related Examples.