Detecting the first non-repeating string in Array in JavaScript

Suppose, we have an array of strings like this where strings might contain duplicate characters −

const arr = ['54gdgdfe3', '434ffd', '43frdf', '43fdhnh', 'wgcxhjny', 'fsdf34'];

We are required to write a JavaScript function that takes in one such array and returns the very first element from the array that contains 0 duplicate characters. If there does not exist any such string, we should return false.

Therefore, let’s write the code for this function −


The code for this will be −

const arr = ['54gdgdfe3', '434ffd', '43frdf', '43fdhnh', 'wgcxhjny', 'fsdf34'];
const isUnique = str => {
   return str.split('').every(el => str.indexOf(el) === str.lastIndexOf(el));
const findUniqueString = arr => {
   for(let i = 0; i < arr.length; i++){
         return arr[i];
   return false;


The output in the console will be −


Updated on: 17-Oct-2020

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