Question 206788 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – extract duplicate characters from a string

I have a homework assignment where I have to extract duplicate characters from a string and place them in another string.
exp:

const str = "love to learn javascript"

the new string would be

const str2 = "love tarnjscip"

I didn’t made any try as I’m a beginner and I don’t have an initial idea how to start (I think the solution is a nested loop)

Can you help me and give me different ways to handle this kind of exercise?

Tags:

4

Answers


  1. 0

    here i created an empty array and i pushed to it every unique letter, then in the next round i check if a letter already added so it means the letter repeated then i call continue to skip to the next round if the letter repeated or i add the letter if it is not.
    hope this works for you.

    const sentence = "love to learn javascript"

const letters = []
let result = ''
for(const item of sentence)
{
  const check = letters.find((i)=>i===item)
  if(check)continue;
  letters.push(item)
  result += item
}
console.log(result)
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  2. 0

    You can use an object to easily keep track of which letters you already encountered.

    const str = "love to learn javascript"

let str2 = "";

let letters = {};

for(let i=0, l=str.length; i<l; ++i) {
  let letter = str[i];
  if(!letters[letter]) { // if the object does not have a property
                         // named after the current letter yet
    str2 += letter; // then add that letter to the result string
  }
  letters[letter] = 1; // set the object property for the current letter
}

console.log(str2)
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  3. 0

    This code iterates through each character in the str string. It checks if the current character is a duplicate by comparing the last occurrence index with the first occurrence index of that character. If they are not equal, it means the character appears more than once.

    const str = "love to learn javascript";
let str2 = "";

for (let i = 0; i < str.length; i++) {
  if (str.lastIndexOf(str[i]) !== str.indexOf(str[i])) {
    if (!str2.includes(str[i])) {
      str2 += str[i];
    }
  }
}

    Demo

    const str = "love to learn javascript";
let str2 = "";

for (let i = 0; i < str.length; i++) {
  if (str.lastIndexOf(str[i]) !== str.indexOf(str[i])) {
    if (!str2.includes(str[i])) {
      str2 += str[i];
    }
  }
}

console.log(str2);
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  4. 0

    You could use Set:

    const r = [...new Set("love to learn javascript").values()].join('');
console.log(r);
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