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JS Coding Question #9: Get Max Character In A String [Challenging]

Interview Question #9:

Write a function that will return the max character in a string.🤔 You may get variation to the question as well like Write a function that will return that most commonly used character in a sentence or similar.

Additional Rules:

  1. Treat lowercase and uppercase the same
  2. Only count alphabetic characters, no symbols and numbers
  3. Return one max character in case of multiple max characters

If you need practice, try to solve this on your own without looking at the solution below.

Feel free to bookmark 🔖 even if you don't need this for now. You may need to refresh/review down the road when it is time for you to look for a new role.

Codepen:

If you want to play around and experiment with the code: https://codepen.io/angelo_jin/pen/abwYGPo

Solution below will cycle on every string and create a map. Once the map is created, cycle on the map and use the variables created to see if the current char has greater count. Assign char and max count accordingly.

// Helper function to remove non alphabetic characters and transform string to lowercase
function normalizeString(str) {
  return str
    .replace(/[^\w]/g, '')
    .toLowerCase()
}

function getMaxChar(str) {
  const charMap = {}
  let max = 0
  let maxChar = ''

  for (let char of normalizeString(str)) {
    if (charMap[char]) {
      charMap[char]++
    } else {
      charMap[char] = 1
    }
  }

  for (let char in charMap) {
    if (charMap[char] > max) {
      max = charMap[char]
      maxChar = char
    }
  }

  return maxChar
}
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Video below if you prefer instead of bunch of text/code 👍😊

Discussion (7)

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inhuofficial profile image
InHuOfficial • Edited

The only issue with your example is the double loop, you can achieve the same with the following which takes advantage of how split works:

99% sure it returns the same as your function.

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frontendengineer profile image
Let's Code Author • Edited

thank you for this solution! Learned something today. I took your example and translate it to more readable form.

function getMaxChar(str){
  let max = 0
  let maxChar = ''
  const normalizedString = str.toLowerCase().replace(/[^a-z']/g, "")

  normalizedString.split('')
    .forEach(char => {
      if (normalizedString.split(char).length > max) {
          max = normalizedString.split(char).length;
          maxChar = char;
       }
    })

  return maxChar;
}
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inhuofficial profile image
InHuOfficial

Yeah sorry, I already had the main part of the function as part of a code snippets library and it is partially minimised due to a mistake I made...I have about 100 snippets that aren't very readable like that!

I have copied the normalisedString.split() etc. part back into my code snippets library so it is readable again, so thanks for that 😀

Maybe I will finally get around to fixing them all as they do come in handy and it just laziness stopping me fixing them!

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frontendengineer profile image
Let's Code Author

LOL dude, nothing to apologize from. You actually improved my solution helping out myself and other folks who will read this post. So thank you and I am glad that you came in and share that snippet. 👍

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