pickPeaks.js

// In this kata, you will write a function that returns the positions and the values of the "peaks" (or local maxima) of a numeric array.

// For example, the array arr = [0, 1, 2, 5, 1, 0] has a peak at position 3 with a value of 5 (since arr[3] equals 5).

// The output will be returned as an object with two properties: pos and peaks. Both of these properties should be arrays. If there is no peak in the given array, 
//   then the output should be {pos: [], peaks: []}.

// Example: pickPeaks([3, 2, 3, 6, 4, 1, 2, 3, 2, 1, 2, 3]) should return {pos: [3, 7], peaks: [6, 3]} (or equivalent in other languages)

// All input arrays will be valid integer arrays (although it could still be empty), so you won't need to validate the input.

// The first and last elements of the array will not be considered as peaks (in the context of a mathematical function, 
//   we don't know what is after and before and therefore, we don't know if it is a peak or not).

// Also, beware of plateaus !!! [1, 2, 2, 2, 1] has a peak while [1, 2, 2, 2, 3] and [1, 2, 2, 2, 2] do not. In case of a plateau-peak, 
// please only return the position and value of the beginning of the plateau. 
// For example: pickPeaks([1, 2, 2, 2, 1]) returns {pos: [1], peaks: [2]} (or equivalent in other languages)

// pickPeaks([3,2,3,6,4,1,2,3,2,1,2,3]), {pos:[3,7], peaks:[6,3]}
// pickPeaks([3,2,3,6,4,1,2,3,2,1,2,2,2,1]), {pos:[3,7,10], peaks:[6,3,2]}
// pickPeaks([2,1,3,2,2,2,2,5,6]), {pos:[2], peaks:[3]}
// [1,2,5,4,3,2,3,6,4,1,2,3,3,4,5,3,2,1,2,3,5,5,4,3]), {pos:[2,7,14,20], peaks:[5,6,5,5]}


function pickPeaks(arr){
  let result = {pos:[],peaks:[]};  
  arr.forEach((el, i, arr) => {
    if(i != 0 && i != arr.length-1) {
      if(el > arr[i-1] && el >= arr[i+1]) {
        result.pos.push(i);
        result.peaks.push(el);
        console.log(result)
        if(el === arr[i+1] && el === arr[arr.length-1]  && result.peaks[result.peaks.length-1] === el){
          result.peaks.pop();
          result.pos.pop();
        }
      } 
    }
  })
  return result;
}