Given a set of possibilities, determine the maximum reward in the possibilities given a certain constraint.

possibilities.js

/* 
For this particular example the constraint is you cannot take two possibilities
that are next to each other. A real world example might be that you cannot invest multiple months
in a row and want to have the best chance at the best ROI. Kind of dumb but the point is 
if there are constraints you want to track the best possible values for every sequence of moves,
only keeping track of the best possible outcomes
*/

const bestOutcome = (arr) => {
    
    // We want arr to be an array of possibilities
    if (!Array.isArray(arr) || arr.length === 0) {
        console.log('Argument is not array or array is empty');
        return;
    }
    
    /* 
    We want to take care of a few important conditions here. We don't want to run an expensive
    iterative function if we don't have to, so if arr is only 1 or 2 indices long we know exactly 
    what value we want
    */
    
    const length = arr.length;
    let nodeArr = []; // We will map out the indices of the possibilities array we choose to take.
    let totalsArr = []; // We calculate our totals here, allowing us to only pass through the possiblities array once.
    let i;
    
    if (arr.length === 1) {
        totalsArr[0] = arr[0];
        nodeArr[0] = 0;
    }
    
    if (arr.length === 2) {
        totalsArr[0] = Math.max(arr[0], arr[1]);
        nodeArr[0] = (arr[0] > arr[1]) ? 0 : 1;
    }
    
    totalsArr[0] = arr[0];
    totalsArr[1] = arr[1];
    let evenTrack;
    let lastTaken = true;
    
    for (i = 2; i < length; i++) {
        totalsArr[i] = Math.max((arr[i] + totalsArr[i-2]), totalsArr[i -1]);
        
        takeThis = (arr[i] + totalsArr[i-2] > totalsArr[i-1]);
        
        if (takeThis) {
          evenTrack = isEven(i);
          
          if (evenTrack) {
            if (evenTrack === lastTaken) {
             nodeArr.push('e');
            }
            else {
              nodeArr.pop();
              nodeArr.push('s', i);
              lastTaken = evenTrack;
            }
          }
          else {
            if (evenTrack === lastTaken) {
             nodeArr.push('o');
            }
            else {
              nodeArr.pop();
              nodeArr.push('s', i);
              lastTaken = evenTrack;
            }
          }
        }
    }
    
    return [nodeArr, totalsArr, Math.max(totalsArr[length-1], totalsArr[length-2])];
}

const isEven = (a) => a % 2 === 0;

Work in progress, trying to get the node array to come out right. Right now I am getting the indexes of where the program decided to switch tracks, which is progress