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up vote 2 down vote favorite

I have found a way to remove repeated characters from a string using regular expressions.

function RemoveDuplicates() {
    var str = "aaabbbccc";
    var filtered = str.replace(/[^\w\s]|(.)\1/gi, "");  
    alert(filtered);
}

Output: abc this is working fine.

But if str = "aaabbbccccabbbbcccccc" then output is abcabc. Is there any way to get only unique characters or remove all duplicates one? Please let me know if there is any way.

share|improve this question
    
Does the order matter? In other words, is it necessary that the first occurrence of the character is the one you save? –  Lindrian Oct 10 '13 at 17:01
    
i want characters in same sequence after remove duplicates one. Only unique one. –  Mike Oct 10 '13 at 17:04

1 Answer 1

up vote 7 down vote accepted

A lookahead like "this, followed by something and this":

> str = "aaabbbccccabbbbcccccc"
"aaabbbccccabbbbcccccc"
> str.replace(/(.)(?=.*\1)/g, "")
"abc"

Note that this preserves the last occurrence of each character:

> str = "aabbccxccbbaa"
"aabbccxccbbaa"
> str.replace(/(.)(?=.*\1)/g, "")
"xcba"

Without regexes, preserving order:

> str.split("").filter(function(x, n, s) { return s.indexOf(x) == n }).join("")
"abcx"
share|improve this answer
    
I asked Mike but he has not answered yet. Your solution is the one I would have gone with, and if you need to preserve order, wouldn't str.split("").reverse().join("") do the trick? –  Lindrian Oct 10 '13 at 17:04
1  
by running this code... string is not coming in same seqeunce. if var str = "aaabbbcccaabbbcccaaaaaaaasa"; output = "bcsa" but i want something like abcs –  Mike Oct 10 '13 at 17:07
    
@Lindrian: yes, that, or some other method from blog.stevenlevithan.com/archives/mimic-lookbehind-javascript –  georg Oct 10 '13 at 17:07

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