Daily JavaScript Challenge #JS-84: Find the First Repeated Character in a String

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Daily JavaScript Challenge: Find the First Repeated Character in a String

Hey fellow developers! 👋 Welcome to today's JavaScript coding challenge. Let's keep those programming skills sharp!

The Challenge

Difficulty: Easy

Topic: String Manipulation

Description

Given a string, find and return the first character that repeats. If there is no such character, return null.

Ready to Begin?

https://www.dpcdev.com/

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Write your solution
Test it against the provided test cases
Share your approach in the comments below!

Want to Learn More?

Check out the documentation about this topic here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set

Join the Discussion!

How did you approach this problem?
Did you find any interesting edge cases?
What was your biggest learning from this challenge?

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This is part of our Daily JavaScript Challenge series. Follow me for daily programming challenges and let's grow together! 🚀

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Top comments (5)

Peter Vivo • Jan 27 • Edited

"owqiqroiqwhfuiffeuuuueqwyuyewquy"
  .split('')
  .find(
    (c,i,list) => c === list[i+1]
  )
;

/** @type {(str:string) => string | undefined} */
const firstRepeat = str => str
  .split('')
  .find(
   (chr ,idx , list) => chr === list[idx + 1]
  )
;

ThatGuyJK🕵🏾‍ • Jan 28

Your code for the first snippet returns 'f' when it should return 'q'

Peter Vivo • Jan 28

"feqnjoiwqejjif".split('').find((c,i,arr) => arr.indexOf(c)<i)

/** @type {(str:string) => string | undefined} */
const firstRepeat = str => str
  .split('')
  .find(
   (chr ,idx , list) => list.indexOf(chr) < idx)
  )
;