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JavaScript: Remove all characters from a given string that appear more than once

JavaScript Basic: Exercise-135 with Solution

Write a JavaScript program to remove all characters from a given string that appear more than once.

Pictorial Presentation:

JavaScript: Remove all characters from a given string that appear more than once.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>Remove all characters from a given string that appear more than once</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function remove_duplicate_cchars(str) {
  var arr_char = str.split("");
  var result_arr = [];

  for (var i = 0; i < arr_char.length; i++) {
    if (str.indexOf(arr_char[i]) === str.lastIndexOf(arr_char[i]))
      result_arr.push(arr_char[i]);
    }

  return result_arr.join("");
}
console.log(remove_duplicate_cchars("abcdabc"));
console.log(remove_duplicate_cchars("python"));
console.log(remove_duplicate_cchars("abcabc"));
console.log(remove_duplicate_cchars("1365451"));

Sample Output:

d
python

364

Flowchart:

Flowchart: JavaScript - Remove all characters from a given string that appear more than once

ES6 Version:

function remove_duplicate_cchars(str) {
  const arr_char = str.split("");
  const result_arr = [];

  for (let i = 0; i < arr_char.length; i++) {
    if (str.indexOf(arr_char[i]) === str.lastIndexOf(arr_char[i]))
      result_arr.push(arr_char[i]);
    }

  return result_arr.join("");
}
console.log(remove_duplicate_cchars("abcdabc"));
console.log(remove_duplicate_cchars("python"));
console.log(remove_duplicate_cchars("abcabc"));
console.log(remove_duplicate_cchars("1365451"));

Live Demo:

See the Pen javascript-basic-exercise-135 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a.
Next: Write a JavaScript program to replace the first digit in a string (should contains at least digit) with $ character.

What is the difficulty level of this exercise?



JavaScript: Tips of the Day

Parameter's value

function getItems(fruitList, ...args, favoriteFruit) {
  return [...fruitList, ...args, favoriteFruit]
}

getItems(["banana", "apple"], "pear", "orange")

...args is a rest parameter. The rest parameter's value is an array containing all remaining arguments, and can only be the last parameter! In this example, the rest parameter was the second parameter. This is not possible, and will throw a syntax error.

function getItems(fruitList, favoriteFruit, ...args) {
  return [...fruitList, ...args, favoriteFruit];
}


getItems(['banana', 'apple'], 'pear', 'orange');
The above example works. This returns the array [ 'banana', 'apple', 'orange', 'pear' ].

Ref: https://bit.ly/3jFRBje