function binary_Search(items, value){  
    var firstIndex  = 0,  
        lastIndex   = items.length - 1,  
        middleIndex = Math.floor((lastIndex + firstIndex)/2);  
  
    while(items[middleIndex] != value && firstIndex < lastIndex)  
    {  
       if (value < items[middleIndex])  
        {  
            lastIndex = middleIndex - 1;  
        }   
      else if (value > items[middleIndex])  
        {  
            firstIndex = middleIndex + 1;  
        }  
        middleIndex = Math.floor((lastIndex + firstIndex)/2);  
    }  
  
 return (items[middleIndex] != value) ? -1 : middleIndex;  
}  
var items = [1, 2, 3, 4, 5, 7, 8, 9];  
console.log(binary_Search(items, 1));     
console.log(binary_Search(items, 5));    