Javascript: Determine if all characters in a string are unique and if not, delete duplicate characters - Stack Overflow

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Have an array set up with a[letter][occurences], but struggling with looping through this array, to check for occurences > 1 and removing the ones that are.

function charFreq(s) {
    var i, j;
    var a = new Array();

    for (j = 0; j < s.length; j++) {
        for (i = 0; i < a.length; i++) {
            if (a[i][0] == s[j]) {
                a[i][1]++;
                break;
            }
        }
        if (i == a.length) {
            a[i] = [s[j], 1];
        }
    }
    return a[i][0];
}
document.write(charFreq("insert string here"));

This is the mess I've e up with so far:

function check(str) {
    var c;
    for (c=0; c < a.length; c++) {
        if(a[c][1] == 1) {
            return true;
            break;
        } else {
            return false;
        }
    }
}

Have an array set up with a[letter][occurences], but struggling with looping through this array, to check for occurences > 1 and removing the ones that are.

function charFreq(s) {
    var i, j;
    var a = new Array();

    for (j = 0; j < s.length; j++) {
        for (i = 0; i < a.length; i++) {
            if (a[i][0] == s[j]) {
                a[i][1]++;
                break;
            }
        }
        if (i == a.length) {
            a[i] = [s[j], 1];
        }
    }
    return a[i][0];
}
document.write(charFreq("insert string here"));

This is the mess I've e up with so far:

function check(str) {
    var c;
    for (c=0; c < a.length; c++) {
        if(a[c][1] == 1) {
            return true;
            break;
        } else {
            return false;
        }
    }
}

• javascript
• string
• unique

Share Follow edited Mar 13, 2016 at 21:55 Robin 7,89422 gold badges3434 silver badges4949 bronze badges asked Jun 24, 2013 at 22:07 JSNewbJSNewb 6522 silver badges77 bronze badges

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7 Answers 7

Sorted by: Reset to default 3

Using ES6 Set:

// :: unique = Array<any>|string => Array<any>
const unique = xs => [...new Set(xs)]

const dedupe = str => unique(str).join('')

console.log(
  unique('foo'), // => ['f', 'o']
  dedupe('foo'), // => 'fo'
)

Don't do it that way.

function noDups( s ) {
  var chars = {}, rv = '';

  for (var i = 0; i < s.length; ++i) {
    if (!(s[i] in chars)) {
      chars[s[i]] = 1;
      rv += s[i];
    }
  }

  return rv;
}

alert(noDups("Shoe fly pie, and apple pan dowdy")); // Shoe flypi,andw

As the length of your string gets longer, your code gets slower by a factor roughly equal to the square of the length of the string.

To delete duplicate characters from an string, you can use the next function that made the user @Cerbrus

function find_unique_characters( string ){
    var unique='';
    for(var i=0; i<string.length; i++){
        if(string.lastIndexOf(string[i]) == string.indexOf(string[i])){
            unique += string[i];
        }
    }
    return unique;
}
console.log(find_unique_characters('baraban'));

If you only want to return characters that appear occur once in a string, check if their last occurrence is at the same position as their first occurrence.

Your code was returning all characters in the string at least once, instead of only returning characters that occur no more than once

Link to the thread of stackoverflow Remove duplicate characters from string ​

Here's a quick way:

str = str.split('').filter(function(v,i,self){
  return self.indexOf(v) == i;
}).join('');

function RemoveDuplicateLetters(input) {
    var result = '', i = 0, char = '';
    while (i < input.length) {
        char = input.substring(i, i+1);
        result += char;
        input = input.replace(char,'');
    }
    return result;
}

I can't see a splice version, so here's one:

function uniqueChars(s) {
  var s = s.split('');
  var c, chars = {}, i = 0;

  while ((c = s[i])) {
    c in chars? s.splice(i, 1) : chars[c] = ++i;
  }
  return s.join('');
}

This assumes only alpha characters, and upper case not equal to lower case.

function uniqueChars(string){
    var i= 0, L= string.length, ustring= '', next;
    while(i<L){
        next= string.charAt(i++);
        if(ustring.indexOf(next)== -1) ustring+= next;
    }
    return ustring.replace(/[^a-zA-Z]/g, '');
}
var s1= 'The quick red fox jumps over the lazy brown dog.';
uniqueChars(s1)

/* returned value: (String) Thequickrdfoxjmpsvtlazybwng */

This returns any unique character-

function uniqueArray(array){
    return array.filter(function(itm, i, T){
        return T.indexOf(itm)== i;
    });
}
var s1= 'The quick red fox jumps over the lazy brown dog.';
uniqueArray(s1.split('')).join('');

/* returned value: (String) The quickrdfoxjmpsvtlazybwng. */

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