how to do descending order prime numbers in javascript?

Question

There's a way I can "invert" my array of prime numbers? or I have to do in other logic way.

There's my code

var primos = [];
for (var i = 0; i <= 100; i++) {
    var fake = false;
    for (var j = 2; j <= i; j++) {
        if (i%j==0 && j!=i) {
            fake = true;
        }
    }
    if (fake === false) {
        primos.push(i);
    }
}
for(i = primos.length; i > 0; i--) {
    console.log(primos[i]);
}

I want the result to be the array but in descending order Like [97, 89, 83, ...]

you want to reverse the array? you can also `unshift` which adds values to the head of the array ... — Jaromanda X, Mar 20 '18 at 02:50
Do you want to reverse the array or have your algorithm outputting the array on order crescent? — Vinicius Santana, Mar 20 '18 at 02:52
You can refer to this if its the second option. https://stackoverflow.com/questions/11966520/how-to-find-prime-numbers-between-0-100 — Vinicius Santana, Mar 20 '18 at 02:53
yeah, have to say, not sure what `decrescent` even means, it's not an English word at all ... how about you specify what your result should be — Jaromanda X, Mar 20 '18 at 02:59
so, unshift **WILL** produce the right result - if it doesn't then the code isn't producing the primes correctly at all — Jaromanda X, Mar 20 '18 at 03:03
wow, it is too - my browsers spell checker doesn't think so :p — Jaromanda X, Mar 20 '18 at 03:03
yep @JaromandaX unshift solve it :)! I get it now, I was trying to use directly in the result — Pedro Sturmer, Mar 20 '18 at 03:06

score 1 · Accepted Answer · answered Mar 20 '18 at 02:57

1

If you want to simply revert the result you can use the Array prototype method reverse:

var primos = [];
for (var i = 0; i <= 100; i++) {
    var fake = false;
    for (var j = 2; j <= i; j++) {
        if (i%j==0 && j!=i) {
            fake = true;
        }
    }
    if (fake === false) {
        primos.push(i);
    }
}
primos = primos.reverse();
for(i = primos.length; i > 0; i--) {
    console.log(primos[i]);
}

Take a look at this other answer for some ideas on other ways to accomplish this:

How to find prime numbers between 0 - 100?

answered Mar 20 '18 at 02:57

Vinicius Santana

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1

use unshift instead of push, no more reverse required :p – Jaromanda X Mar 20 '18 at 02:58
or loop i from 100...2 :p – Jaromanda X Mar 20 '18 at 02:59

how to do descending order prime numbers in javascript?

1 Answers1