Cassidoo Challenge - Find Local Peaks

findLocalPeaks.js

/**
 * Returns array of indices of local peaks in given array
 *
 * @param {array of integers} arr - The array where we will discover peaks (hopefully)
 * @return {array of integers} peaks - indices of local peaks in @param arr.
 */

const localPeaks = (arr) => {
  const peaks = [];

  arr.forEach((element, index) => {
    const prevIndex = index - 1;
    const nextIndex = index + 1;
    if (prevIndex >= 0 && nextIndex < arr.length) {
      if (element > arr[prevIndex] && element > arr[nextIndex]) {
        peaks.push(index);
      }
    }
  });

  return peaks;
};

console.log(localPeaks([4, 6, 5, 9, 11, 3, 90, 45])); // [1, 4, 6]