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

var str = 'anaconda'.split('');
var rmDup = str.filter(function(val, i, str){
     return str.lastIndexOf(val) === str.indexOf(val);
});
console.log(rmDup); //prints ["c", "o", "d"]

Please verify here: https://jsfiddle.net/jmgy8eg9/1/

Answer 2

Just wanted to add my solution for fun:

function removeDoubles(string) {
  var mapping = {};
  var newString = '';

  for (var i = 0; i < string.length; i++) {
    if (!(string[i] in mapping)) {
      newString += string[i];
      mapping[string[i]] = true;
    }
  }
  return newString;
}

Answer 3

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

Answer 4

    function RemDuplchar(str)
{
    var index={},uniq='',i=0;
    while(i<str.length)
    {
        if (!index[str[i]])
        {
         index[str[i]]=true;
         uniq=uniq+str[i];
        }
            i++;
    }
    return uniq;
} 

Answer 5

Just came across a similar issue (finding the duplicates). Essentially, use a hash to keep track of the character occurrence counts, and build a new string with the "one-hit wonders":

function oneHitWonders(input) {
    var a = input.split('');
    var l = a.length;
    var i = 0;
    var h = {};
    var r = "";

    while (i < l) {
        h[a[i]] = (h[a[i]] || 0) + 1;

        i += 1;
    }

    for (var c in h) {
        if (h[c] === 1) {
            r += c;
        }
    }

    return r;
}

Usage:

var a = "anaconda";
var b = oneHitWonders(a); // b === "cod"

Answer 6

We can remove the duplicate or similar elements in string using for loop and extracting string methods like slice, substring, substr

Example if you want to remove duplicate elements such as aababbafabbb:

var data = document.getElementById("id").value
for(var i = 0; i < data.length; i++)
{
    for(var j = i + 1; j < data.length; j++)
    {
        if(data.charAt(i)==data.charAt(j))
        {
            data = data.substring(0, j) + data.substring(j + 1);
            j = j - 1;
            console.log(data);
        }
    }
}

Please let me know if you want some additional information.