count duplicate word in js code example

Example 1: how to check for duplicate syntax in javascript

let strArray = [ "q", "w", "w", "w", "e", "i", "u", "r"];
let findDuplicates = arr => arr.filter((item, index) => arr.indexOf(item) != index)

console.log(findDuplicates(strArray)) // All duplicates
console.log([...new Set(findDuplicates(strArray))]) // Unique duplicates

Example 2: how to find repeated characters in a string in javascript

const getRepeatedChars = (str) => {
  const strArr = [...str].sort();
  const repeatedChars = [];
  for (let i = 0; i < strArr.length - 1; i++) {
      if (strArr[i] === strArr[i + 1]) repeatedChars.push(strArr[i]);
  }
  return [...new Set(repeatedChars)];
};

getRepeatedChars("aabbkdndiccoekdczufnrz"); // ["a", "b", "c", "d", "k", "n", "z"]