get all prime numbers javascript code example

Example 1: javascript find prime number

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

console.log(test_prime(37));

Example 2: javascript write all the prime numbers from 1 to 100

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

function display(n) {
    var arr = [2];
    for ( var i = 3; i < n; i+=2 ) {
        if ( isPrime(i) ) {
            arr.push(i);
        }
    }
    console.log(arr); // use arr result on your own
}

display(100);


//Added Functionality

function prime(n,flag) {
    ( typeof flag === "undefined" || flag === false ) ? flag = false : flag = true;

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

    if ( flag ) {
        var arr = [2];
        for ( var i = 3; i <= n; i+=2 ) {
            if ( isPrime(i) ) {
                arr.push(i);
            }
        }
        return arr;
    } else {
        return isPrime(n);
    }
}