Using forEach Loop Generating prime number in Javascript between 1 to 50

Question

Here's my code but my answer is not that which i want..

Please Check This and give me a solution to get prime number using Foreach Loop b/w 1-50

Thanks In Advance :)

function isPrime(num) {
    for ( var i = 2; i < num; i++ ) {
        if ( num % i === 0 ) {
            return false;
        }
    }
    return true;
}
    var txt = "";
    function shown(n) {
        var arr = [2];
        arr.forEach(myFunction);

document.getElementById("foreach").innerHTML = txt;
// document.getElementById('forLoop').innerHTML = arr; // use arr result on your own
}
function myFunction(arr, index, array) {

var i;
var arr = [2];

if ( isPrime(i) ) {
    arr.push(i);
      }
  txt += arr + "<br>"; 
}

shown(50);

Might try here first: https://meta.stackoverflow.com/questions/334822/how-do-i-ask-and-answer-homework-questions — Twisty, Aug 20 '20 at 05:41
Welcome to Stack Overflow. What errors are you getting and what output are you expecting? — Twisty, Aug 20 '20 at 05:43
I think you need to first logically break down your problem into small steps. Then, when you try solving the steps one-by-one, you can come up with more specific problem with, maybe, one specific step. And with that specific problem, you can probably find solution online already. — Koala Yeung, Aug 20 '20 at 05:48
@Twisty i have explained before in my question.. array is between 1 to 50 numbers — raoabdullah07, Aug 20 '20 at 06:39
@AbdullahRao your example does not show this. you have an array with a single element: `[2]`. — Twisty, Aug 20 '20 at 06:47
but in shown(50) it shows that array starts with 2 and ends on 50 — raoabdullah07, Aug 20 '20 at 06:50
@AbdullahRao You just pasted your whole code here. There are many logical steps in it that you can verify one-by-one. Thay way you'd be able to submit a more specific question than this "I don't know how to do the whole thing" type question. — Koala Yeung, Aug 26 '20 at 08:11

Koala Yeung · Answer 1 · 2020-10-28T06:22:39.460

This is probably a too-advanced answer for a homework of this level, but technically it follows the rules (use Array.forEach) and it works.

The primes() generates new primes based on previous primes. So it won't test the reminder of all integers, thus more effecient. There are several arrow function uses, too, to keep things short. If you indeed use this answer, please try to read the relevant documentations and learn:

Seriously, try to think step-by-step. That's how you learn anything.

function* primes() {
  const previous = [];

  for (let i = 2; true; i++) {
    let isPrime = true;
    for (let p of previous) {
      if (i % p === 0) {
        isPrime = false;
        break;
      }
    }
    if (isPrime) {
      previous.push(i);
      yield i;
    }
  }
}

function* takeUntil(cb, iter) {
  for (let val of iter) {
    if (cb(val)) {
      return;
    }
    yield val;
  }
}

function showArrayIn(arr, container) {
  arr.forEach(p => container.innerHTML += `${p},<br/>`); // technically, we used Array.forEach.
}

showArrayIn(
  // get the prime number array declarativly 
  Array.from(takeUntil(n => n >= 50, primes())),
  // show in the container specified
  document.getElementById("results")
);

Primes:
<div id="results"></div>

score 0 · Answer 2 · answered Aug 20 '20 at 05:54

0

function primeFactorsTo(max)
{
    var store  = [], i, j, primes = [];
    for (i = 2; i <= max; ++i) 
    {
        if (!store [i]) 
          {
            primes.push(i);
            for (j = i << 1; j <= max; j += i) 
            {
                store[j] = true;
            }
        }
    }
    return primes;
}

console.log(primeFactorsTo(5));

console.log(primeFactorsTo(15));

answered Aug 20 '20 at 05:54

Nikhilesh Agrawal

223
1
6

See my question above – raoabdullah07 Aug 20 '20 at 06:11

Twisty · Answer 3 · 2020-08-20T07:49:30.930

0

Consider the following example.

function isPrime(num) {
  if (num === 1) {
    return false;
  } else if (num === 2) {
    return true;
  } else {
    for (var x = 2; x < num; x++) {
      if (num % x === 0) {
        return false;
      }
    }
    return true;
  }
}

function shown(n) {
  var list = [];
  for (var i = 1; i <= n; i++) {
    list.push(i);
  }
  list.slice().reverse().forEach(function(n, k, o) {
    if (!isPrime(n)) {
      list.splice(o.length - 1 - k, 1);
    }
  });
  document.getElementById("show").innerHTML = list;
}

shown(50);

Prime: <p id="show"></p>

edited Aug 20 '20 at 07:49

answered Aug 20 '20 at 05:54

Twisty

30,304
2
26
45

Please use ForEach Loop in this program, – raoabdullah07 Aug 20 '20 at 06:09
@AbdullahRao updated. – Twisty Aug 20 '20 at 06:46
Thanks Dear, But 2 is also a prime number – raoabdullah07 Aug 20 '20 at 06:49
1

This is just showing odd numbers. Not prime numbers. – Koala Yeung Aug 20 '20 at 06:50
Yes it showing me odd numbers these are are not prime numbers – raoabdullah07 Aug 20 '20 at 06:54

score 0 · Accepted Answer · answered Aug 20 '20 at 06:55

I Think so this is the correct answer which i deserve.. It is code lover short and aggressive

function primes(limit)
{
  var prime=[], i=1;
  while (++i < limit+1) prime.reduce((a,c)=>(i%c)*a,1) && prime.push(i);
  prime.unshift(2);
  return prime;
}
[50].forEach(n=>document.getElementById('foreach').innerHTML=(`${primes(n)}`));

Using forEach Loop Generating prime number in Javascript between 1 to 50

4 Answers4