CODEWITHSUNDEEP
javascriptarraysvalidation
nyoung
nyoung

Reputation: 13

How to validate if a letter in an array is repeated?

I want to validate that a string within an array is not repeated more than 3 times, that is:

let array = ['A', 'A', 'A', 'B']
let array2 = ['A', 'A', 'A', 'A', 'B'] <-- Not valid

That the code does not continue to work, if the array it receives has values that are repeated those times

Thank you

Upvotes: 1

Views: 86

Answers (3)

Reyno
Reyno

Reputation: 6525

You can use array.some() in combination with array.filter() to check if a value only exists an x amount of times.

const array = ['A', 'A', 'A', 'B'];
const array2 = ['A', 'A', 'A', 'A', 'B'];

const isValid = (arr, limit) => {
  return !arr.some((char) => (
    arr.filter((ch) => ch === char).length > limit
    // use the next line for a case insensitive check
    // arr.filter((ch) => ch.toLowerCase() === char.toLowerCase()).length > limit
  ));
}

console.log(isValid(array, 3));
console.log(isValid(array2, 3));

Upvotes: 3

MauriceNino
MauriceNino

Reputation: 6757

You can count all the letters using reduce and then check those, like so:

let array = ['A', 'A', 'A', 'B'];
let array2 = ['A', 'A', 'A', 'A', 'B'];

const allElementsExistUpToN = (arr, n) => {
  const counts = arr.reduce((acc, el) => {
    acc[el] = acc[el] == undefined ? 1 : acc[el] +1;
    return acc;
  }, {});
  return !Object.values(counts).some(c => c > n);
}

console.log(allElementsExistUpToN(array, 3));
console.log(allElementsExistUpToN(array2, 3));

Upvotes: 0

Nina Scholz
Nina Scholz

Reputation: 386756

You could take a closure over the count of the last string and check the count or reset the count to one.

const
    check = array => array.every(
        (c => (v, i, { [i - 1]: l }) => l === v ? c++ < 3 : (c = 1))
        (0)
    );

console.log(check(['A', 'A', 'A', 'B']));
console.log(check(['A', 'A', 'A', 'A', 'B']));

Upvotes: 0

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