function gcd_more_than_two_numbers(input) {  
  if (toString.call(input) !== "[object Array]")    
        return  false;    
  var len, a, b;  
    len = input.length;  
    if ( !len ) {  
        return null;  
    }  
    a = input[ 0 ];  
    for ( var i = 1; i < len; i++ ) {  
        b = input[ i ];  
        a = gcd_two_numbers( a, b );  
    }  
    return a;  
}  
  
function gcd_two_numbers(x, y) {  
  if ((typeof x !== 'number') || (typeof y !== 'number'))   
    return false;  
  x = Math.abs(x);  
  y = Math.abs(y);  
  while(y) {  
    var t = y;  
    y = x % y;  
    x = t;  
  }  
  return x;  
}  
console.log(gcd_more_than_two_numbers([3,15,27]));  
console.log(gcd_more_than_two_numbers([5,10,15,25]));