Remove duplicate characters using Javascript

Question

I am trying to achieve the following output but keep coming up short. Not sure I am taking the correct approach on this one. I looking to only allow only letters in the field also.

Html:

<input type="text" id="input-field" onkeyup="myFunction()">

Js:

const remDup= s=> s.split("").filter((e,i,f)=>f.indexOf(e)==i).sort().join("")
const myFunction = (e) => {
  let str = document.getElementById('input-field').value
  //Only allow letters no other characters
  if(("abcdefghijklmnopqrstuvwxyz ").indexOf(String.fromCharCode(e.keyCode))===-1){
    e.preventDefault();
    return false;
  }
  console.log(remDup(str))
}

CertainPerformance · Accepted Answer · 2019-01-08 00:37:31Z

The logic will probably be better if you iterate over the string, filtering it by whether the lower-case version of the character being iterated over exists in a Set that you add to on every iteration.

Note that you do need to transform the character to lower-case before you test, which your current code isn't doing (nor does it look to be checking for duplicate characters):

const myFunction = (e) => {
  const input = document.getElementById('input-field').value;
  const alphaInput = input.replace(/[^a-z]/gi, '');
  const haveChars = new Set();
  const outputArr = [...alphaInput].filter((char) => {
    const lower = char.toLowerCase();
    if (haveChars.has(lower)) {
      return false;
    } else {
      haveChars.add(lower);
      return true;
    }
  });
  const strWithoutDupes = outputArr.join('');
  console.log(strWithoutDupes);
}

<input type="text" id="input-field" onkeyup="myFunction()" value="AbraCadABraAlakAzam">

Andy · Accepted Answer · 2019-01-08 19:28:10Z

1

There's a slightly shorter version that you can write using Set:

const input = document.getElementById('input-field');
input.addEventListener('keyup', handleKeyUp, false);
const re = /[a-zA-Z]/;

function handleKeyUp(e) {

  // `reduce` over the value comparing the current element
  // to a lowercase list of previous iterated letters  
  const deduped = [...e.target.value].reduce((acc, el) => {
    const k = el.toLowerCase();
    if (!re.test(el) || acc.tmp.has(k)) return acc;
    acc.tmp.add(k);
    acc.out.push(el);
    return acc;
  }, { out: [], tmp: new Set() }).out.join('');
  console.log(deduped);
}

<input type="text" id="input-field" value="AbraCadABraAlakAzam">

edited Jan 8, 2019 at 19:28

answered Jan 8, 2019 at 1:12

Andy

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6 Comments

user992731 Over a year ago

Letters are still being duplicated - "AbraCdBlkzm"

Andy Over a year ago

It just verifies lowercase letters now. @user992731. I assume that's what you mean.

user992731 Over a year ago

Upper and lower. Desired output is ""AbrCdlkzm". Big fan of this shorter version

Andy Over a year ago

So if there's an uppercase A there shouldn't be a lowercase a.

user992731 Over a year ago

I only want to keep the first occurrence regardless of case.

|

Special Character · Accepted Answer · 2019-01-08 00:53:53Z

0

Here is a solution that solves your problem in O(n) time and space.

const removeDups = (léString) => {
  const strArray = léString.split('')
  const charsSeen = {}
  let stripped = ''
  strArray.forEach(char => {
    if (!charsSeen[char.toLowerCase()]) {
      stripped += char
      charsSeen[char.toLowerCase()] = true
    }
  })

    return stripped
  }

  console.log(removeDups('AbraCadABraAlakAzam'))

answered Jan 8, 2019 at 0:53

Special Character

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