var library = [   
   { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254},  
   { author: 'Steve Jobs', title: 'Walter Isaacson', libraryID: 4264},  
   { author: 'Suzanne Collins', title: 'Mockingjay: The Final Book of The Hunger Games', libraryID: 3245}  
   ];  
  
function property_value(array, property_key) {  
    var arr = [],  
        index = -1,  
        arrlen = array.length,array_items;  
  
    while (++index < arrlen) {  
        array_items = array[index];  
  
  if (array_items.hasOwnProperty(property_key))   
      {  
     arr[arr.length] = array_items[property_key];  
      }  
    }  
  
    return arr;  
}  
  
console.log(property_value(library, 'title'));  
  
console.log(property_value(library, 'author'));