var getPrimeNumber = function(n) {
    if(n === 1) { return "";}
    else if(n == 2) { return 2;}
    else if(n == 3) { return 3;}
    else {
        for(i=Math.floor(Math.sqrt(n));i>=2;i--){
            //console.log(i);//maybe another var in here?
                if(n%i !==0 && n%2 !==0 && n%3 !== 0) {return n;} // 25/Math.sqrt(25) will be equal to zero this is what gives me 25 !!!
        }
        }
};

function isPrime(number) {
    var start = 2;
    while (start <= Math.sqrt(number)) {
        if (number % start++ < 1) return false;
    }
    return number > 1;
}

if(n%i !==0 && n%2 !==0 && n%3 !== 0)

if(n%2 !==0 && n%2 !==0 && n%3 !== 0)

function(n) {
    if(n === 1) { return false;}
    else if(n == 2) { return true;}
    else if(n == 3) { return true;}
    else {
        for(i=Math.floor(Math.sqrt(n));i>=2;i--){
            //console.log(i);//maybe another var in here?
                if(n%i ==0 || n%2 ==0 || n%3 == 0) {return false;}
        }
        }
    return true;
};

var p = prompt("Insert a number for check","");
var x = " is a prime number";
for(i=2; i<p; i++){
    if(p%i === 0){
        x = " is a composite number";
        break;
    }
}
alert(p+x);

let CalcToNum=1000;

console.log("Calculating until "+CalcToNum+"...");
var prim = [];
for(var i=2; i<CalcToNum; i++)
{
    var isPrim=true;
    if (prim.length>0)
    {
        for(var j=0; j<prim.length; j++)
        {
            if ((i % prim[j])===0)
            {
                isPrim=false; break;
            }
        }
    }
    if (isPrim)
    {
        prim.push(i);
    }
}

console.log("Prim numbers:");
for(var i=0; i<prim.length; i++)
{
    console.log(prim[i]);
}
console.log("Found "+prim.length+" numbers.");