Combinations of strings up to a certain number of elements

combinations.ts

export default function combinations(items: Array<string>, items_length: number, n: number): Array<string> {
  const result = [];

  const getCombinations = (x, n, m = []) => {
    if (n <= 0) {
      return m
    }
    for (var i = 0; i < items_length; i++) {
      const value = getCombinations(x, n - 1, [...m, items[i]]);

      const hasDuplicates = (arr) => arr.length !== new Set(arr).size;
      if (!hasDuplicates(value)) {
        result.push(value);
      }
    }
    return m;
  }
  getCombinations(items.length, n);

  return result.filter(items => items.length == n);
}

index.ts

import combinations from '@/utils/combinations';

SEO_TERMS = ["a", "b", "c", "d", "e"]

combinations(SEO_TERMS, SEO_TERMS.length, 1)
combinations(SEO_TERMS, SEO_TERMS.length, 2)
combinations(SEO_TERMS, SEO_TERMS.length, 3)