My solution to codility test GenomicRangeQuery: https://app.codility.com/programmers/lessons/5-prefix_sums/genomic_range_query/

genomic-range-query.js

/**
 * A DNA sequence can be represented as a string consisting of the letters A, C, G and T,
 * which correspond to the types of successive nucleotides in the sequence. Each nucleotide
 * has an impact factor, which is an integer. Nucleotides of types A, C, G and T have impact
 * factors of 1, 2, 3 and 4, respectively. You are going to answer several queries of the form:
 * What is the minimal impact factor of nucleotides contained in a particular part of the given DNA sequence?
 *
 * The DNA sequence is given as a non-empty string S = S[0]S[1]...S[N-1] consisting of N characters.
 * There are M queries, which are given in non-empty arrays P and Q, each consisting of M integers.
 * The K-th query (0 ≤ K < M) requires you to find the minimal impact factor of nucleotides contained
 * in the DNA sequence between positions P[K] and Q[K] (inclusive).
 *
 * Approach:
 * for each range find occurence of A,C,G,T char in range and return corresponding value
 */

const solution = (S, P, Q) => {
  const genMap = {
    A: 1,
    C: 2,
    G: 3,
    T: 4,
  }
  const sStr = 'ACGT'
  const res = []
  for (let i = 0; i < P.length; i++) {
    const start = P[i]
    const end = Q[i] + 1
    const slice = S.slice(start, end)
    let min
    for (let i = 0; i < 4; i++) {
      const char = sStr[i]
      if (slice.indexOf(char) > -1) {
        min = genMap[char]
        break
      }
    }
    res.push(min)
  }
  return res
}