Need Regex that check at least 4 different character in string

Question

I need Regex that checks if a String has at least 4 unique characters. For example, if a string is "test" then it fails because it have three different chars but if a string is "test1" then it passes.

Do **Not** Use a "regular expression" for this. A regular expression **cannot handle this problem** well. (Yes, it's *possible*, fsvo, but it's a nightmare and limited to a relatively small upper-bound length.) — , Mar 19 '12 at 06:07

jfriend00 · Answer 1 · 2012-03-19T06:16:28.883

6

I'm not sure how to do that with a regex, nor would I expect that to be a good way to solve the problem. Here's a more general purpose function with regular javascript:

function countUniqueChars(testVal) {
    var index = {};
    var ch, cnt = 0;
    for (var i = 0; i < testVal.length; i++) {
        ch = testVal.charAt(i);
        if (!(ch in index)) {
            index[ch] = true;
            ++cnt;
        }
    }
    return(cnt);
}

function hasFourUniqueChars(testVal) {
    return(countUniqueChars(testVal) >= 4);
}

You can see it work here: http://jsfiddle.net/jfriend00/bqBRv/

edited Mar 19 '12 at 06:16

answered Mar 19 '12 at 06:08

jfriend00

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@ChuckNorris "Chuck Norris after dentist" – mowwwalker Mar 19 '12 at 06:16
@jfriend00, What's with charAt() instead of indexing? Is it faster? – mowwwalker Mar 19 '12 at 06:18
@Walkerneo - I've just gotten in the habit of using `.charAt()`. [This other SO question/answer](http://stackoverflow.com/questions/5943726/string-charatx-or-stringx) suggests there are reasons why `.charAt()` is better than array notation for a bunch of reasons, most notably that older versions of IE don't like the array notation. – jfriend00 Mar 19 '12 at 06:22

score 1 · Answer 2 · answered Mar 19 '12 at 06:19

1

If you are open to using additional libraries, undescore.js provides some utility functions that can make this a very short and sweet query:

function countUniqueCharacters(value) {
  return _.uniq(value.split("")).length;
}

answered Mar 19 '12 at 06:19

Chris Pitman

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gayavat · Answer 3 · 2012-03-19T06:43:29.447

0

var str = "abcdef"
var counter = 0; 
hash = new Object(); 
var i;
for(i=0; i< str.length; i++){
  if(!hash[str.charAt(i)]){
    counter +=1; hash[str.charAt(i)]=true
  }
}

if(counter < 4){
  console.log("error");
}

edited Mar 19 '12 at 06:43

answered Mar 19 '12 at 06:22

gayavat

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Doesn't this ignore the last character? – Chris Pitman Mar 19 '12 at 06:25
No. last symbol of string has string.length - 1 position – gayavat Mar 19 '12 at 06:34
1

But you only interate up to string.length - 2, notice the "i< string.length -1". This is part of why I dislike explicit for loops, people mess them up all the time. – Chris Pitman Mar 19 '12 at 06:39

Need Regex that check at least 4 different character in string

3 Answers3