function char_count(str, letter)   
{  
 var letter_Count = 0;  
 for (var position = 0; position < str.length; position++)   
 {  
    if (str.charAt(position) == letter)   
      {  
      letter_Count += 1;  
      }  
  }  
  return letter_Count;  
}  
  
console.log(char_count('w3resource.com', 'o'));