Unique letters in string

Hi,
Is there any method or property in javascript to display unique letters of a string???

Hi Bhargavi,

U need to code. No methods.

Hint: For this use javascript ASCII functions,fromCharCode() and charCodeAt() to solve. input string from user, in first step fill all inputted ASCII character position with zero. then increment those values whenever the same character appears..... then take the count of character positions whose value equal to '1'.