Remove duplicate characters from string

Question

I have to make a function in JavaScript that removes all duplicated letters in a string. So far I\'ve been able to do this: If I have the word \"anaconda\" it shows me as a

Answer 1

I have 3 loopless, one-line approaches to this.

Approach 1 - removes duplicates, and preserves original character order:

var str = "anaconda";
var newstr = str.replace(new RegExp("[^"+str.split("").sort().join("").replace(/(.)\1+/g, "").replace(/[.?*+^$[\]\\(){}|-]/g, "\\$&")+"]","g"),"");
//cod

Approach 2 - removes duplicates but does NOT preserve character order, but may be faster than Approach 1 because it uses less Regular Expressions:

var str = "anaconda";
var newstr = str.split("").sort().join("").replace(/(.)\1+/g, "");
//cdo

Approach 3 - removes duplicates, but keeps the unique values (also does not preserve character order):

var str = "anaconda";
var newstr = str.split("").sort().join("").replace(/(.)(?=.*\1)/g, "");
//acdno